Fix Hubspot Outlook desktop add-in error: Application cannot be started

If you use Hubspot with the Outlook desktop client, you may see the error message “Application cannot be started. Contact the application vendor” when trying to install or open the sales add-in. This guide walks you through the exact steps to diagnose and fix the issue so you can get your Hubspot add-in working again.

What causes the Hubspot Outlook add-in error?

This specific error in Outlook typically appears when a required component is missing or corrupted on your Windows machine. For the Hubspot sales Outlook desktop add-in, the most common cause is a problem with the ClickOnce trust prompt configuration in the Windows registry.

When the ClickOnce trust prompt is disabled or misconfigured, Windows blocks Outlook add-ins that rely on this technology. As a result, the Hubspot add-in cannot start and Outlook shows the generic message telling you to contact the application vendor.

Before you start: check basic Outlook and Hubspot requirements

Before making any changes, verify that your system meets the standard requirements for the Outlook desktop add-in used with Hubspot:

• Supported version of Microsoft Outlook for Windows.
• Stable internet connection for Hubspot to sync email activity.
• Windows user account with permission to modify registry keys (or access to IT support).

If all of these are in place and the error persists, continue with the detailed repair steps below.

Step-by-step fix for the Hubspot Outlook desktop add-in

The recommended fix for this error is to import a trusted ClickOnce configuration into the Windows registry. This changes how Windows treats ClickOnce applications, including the Hubspot sales add-in, and usually resolves the launch problem immediately.

1. Download the ClickOnce registry file from Microsoft

Microsoft provides an official registry file that restores the default trust prompt behavior for ClickOnce applications. To use it for your Hubspot setup, follow these steps:

1. Open your browser in Windows.
2. Go to the official Microsoft documentation page for ClickOnce trust prompt behavior. This page includes a downloadable .reg file.
3. Download the registry file to a location you can easily find, such as your Desktop or Downloads folder.

This registry file will enable the prompts required for Outlook to correctly start applications like the Hubspot add-in.

2. Back up your Windows registry (recommended)

Any change to the registry can affect your system. Before importing the file that will help Hubspot work correctly, create a backup:

1. Press Windows + R to open the Run dialog.
2. Type regedit and press Enter to open the Registry Editor.
3. In the Registry Editor, click File > Export.
4. Select All under Export range.
5. Choose a safe location and name for the backup, then click Save.

With this backup, you can restore the registry if something goes wrong while you troubleshoot the Hubspot error.

3. Import the ClickOnce trust prompt registry file

Now you can apply the settings that allow Outlook to start ClickOnce applications, including Hubspot:

1. Locate the downloaded .reg file in File Explorer.
2. Right-click the file and choose Open or double-click it.
3. If prompted by User Account Control, click Yes to allow changes.
4. When Windows asks whether you want to continue, review the warning and click Yes to add the information to the registry.
5. Click OK when the confirmation message appears.

The new trust prompt configuration is now in place and should allow the Hubspot add-in to start without triggering the previous error.

4. Restart Outlook and test the Hubspot add-in

After importing the registry settings, you must restart Outlook to apply the changes:

1. Completely close Outlook.
2. Wait a few seconds to ensure all Outlook processes have ended.
3. Reopen Outlook.
4. Look for the Hubspot sales add-in in your ribbon or in the list of add-ins.
5. Try to open or use the add-in as you normally would.

In most cases, the “Application cannot be started. Contact the application vendor” message will no longer appear, and the Hubspot add-in will load correctly.

Additional troubleshooting for Hubspot Outlook issues

If the issue continues after changing the ClickOnce settings, there are a few more areas you can review to restore proper Hubspot functionality in Outlook.

Check Outlook add-in status

Confirm that Outlook recognizes the Hubspot add-in and that it is enabled:

1. In Outlook, go to File > Options.
2. Click Add-ins in the left sidebar.
3. Look for the Hubspot sales add-in in the list.
4. At the bottom, next to Manage, choose COM Add-ins and click Go.
5. Ensure the checkbox for the Hubspot add-in is selected.

If the add-in is disabled, enable it and restart Outlook again.

Repair or reinstall the Hubspot add-in

Corrupted installation files can also trigger Outlook errors. If the registry fix did not solve your problem, try reinstalling the Hubspot add-in:

1. Remove the current sales add-in from Outlook.
2. Download the latest Hubspot Outlook desktop add-in from your Hubspot account.
3. Run the installer, following each step carefully.
4. Open Outlook and verify the add-in appears and loads successfully.

A clean installation often resolves persistent issues that the registry change alone does not fix.

When to contact IT or Hubspot support

If you do not have administrative rights on your computer, you may be unable to import the ClickOnce registry file yourself. In that case:

• Share these steps with your internal IT team.
• Ask them to review the ClickOnce trust prompt configuration and test the Hubspot add-in after applying the registry changes.

If your company has complex security policies or custom group policies, your IT team may need to adjust those settings as well to allow the Hubspot add-in to run.

For unresolved issues, you can also contact Hubspot support. Provide them with details about your Outlook version, Windows version, and any steps already taken, including the ClickOnce registry update.

Official resource for the Hubspot Outlook error

For reference and verification of the solution, you can review the official Hubspot knowledge base article about this error. The original instructions are available here: Hubspot Outlook desktop install error documentation.

Get more help with Hubspot and Outlook integrations

If you manage a larger sales team or complex CRM workflows, you may want expert assistance to optimize how Hubspot and Outlook work together, including deployment, training, and ongoing support for sales tools.

Specialized consultants can help you:

• Design scalable email tracking and logging processes.
• Set up consistent Hubspot add-in deployment across multiple devices.
• Document internal procedures for troubleshooting Outlook and Hubspot issues.

For advanced CRM strategy and technical support around marketing and sales platforms, you can explore services from Consultevo, which provides consulting on implementations and optimization.

Summary: restore your Hubspot Outlook add-in quickly

The error “Application cannot be started. Contact the application vendor” can stop your sales team from logging and tracking email activity with Hubspot. In most cases, you can resolve it by:

1. Downloading the official ClickOnce trust prompt registry file from Microsoft.
2. Backing up your registry before making changes.
3. Importing the registry file to restore ClickOnce behavior.
4. Restarting Outlook and confirming the Hubspot add-in is enabled.
5. Repairing or reinstalling the add-in if issues persist.

Following these steps should help you quickly restore the Hubspot Outlook desktop integration and keep your email activity flowing into your CRM without disruption.

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