Outlook Sales Tools "this add-in could not be started"

[MHoskins]

Hello.

We recently as a company started using Hubspot, and while the version downloaded from their website does not work for our organization, getting it directly from the store in Outlook works fine. Except for one user. When they load up the plugin, they get the message "this add-in could not be started. Close this dialog box to ignore the problem, or click Restart to try again" 
We have uninstall and reinstalled the plugin. We've made sure both the OS and Outlook are fully updated. We've enabled protected mode in IE. Every other user can use it just fine, and there is no difference between their configuration and the problem user. 
I was hoping someone might have a suggestion. 

[natsumimori]

Hi @MHoskins ,

Thank you for reaching out to the HubSpot Community!

Could you have your user try the following?

1. Go to File > Options > COM Add-ins > Go and disable all com add-ins - to make sure it's not a conflicting add-in
2. Double-check the Internet Settings for the Restricted Sites Zone:
   
3. Try repairing Outlook (Microsoft support documentation)

After this and if your user still gets an error "this add-in could not be started", I highly encourage you to have this user directly reach out to the Technical Support via phone call (Please see this documentation for how to reach out). Since the error only happens to this particular user, the cause of the issue should be very specific. Hence, it's best for this user to directly connect with Support team for further troubleshooting.

(I see that you put "Professional" label, with Pro subscription your user can reach out to Support via phone call!)