HubSpot Sales for Outlook install error: 'Customized functionality in this application will not work...'

You may encounter the following error message when attempting to install the HubSpot Sales Outlook desktop add-in:

Customized functionality in this application will not work because the certificate used to sign the deployment manifest for Sidekick for Outlook or its location is not trusted.

To resolve this error:

1. Open the Control panel on your Windows device, then use the search bar to look up and select Internet Options.
2. In the Internet Options dialog box, click the Security tab.
3. Select the Trusted sites icon.
4. Click Sites.
5. Add each of the following URLs to the Add this website to the zone field. Click Add after entering each one:
   • https://dl.getsidekick.com
   • https://app.getsidekick.com
   • https://app.hubspot.com

6. Once you've added all three URLs, click Close.
7. Download and run the HubSpot Sales Outlook desktop add-in installer again.
   
   

If the error persists, try the following steps. You may require your IT team's assistance.

1. Check out Microsoft's documentation in the Enabling the ClickOnce Trust Prompt section to manually fix your registry.
2. Access your registry editor and go to the following folder:

3. [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
\Internet Settings]

4. Right-click the DisableCachingOfSSLPages key, and then, click Modify.
5. Set the Value data to 00000000 and click OK.