For instances when you try to reinstall Collabspot Connect add-in but you are still getting the old version. Please check in your Outlook application if an add-in was installed in Admin-manage Add-ins. This means that all add-ins for Outlook are managed by your Office 365 administrator.
The image below shows when an add-in is managed by your Office 365 admin.
Check if your Outlook has Admin Managed Add-ins
1. Go to your Outlook application. Click the Store button then click on Admin-managed button.