I have Timeslips Premium and Outlook 2019 set up on a new Dell laptop (Windows 10).  After completing our billing, Timeslips showed invoices having been sent via email.  Outlook, however didn't send them. Looking at the Add-In Options page in Outlook, the Timeslips Add-in was shown as Inactive.  I went to the Manage Add-ins page.  Timeslips Add-In for Outlook was shown as an available add-in, but when i checked the box to activate it, closed Outlook and then restarted it, the add-in again was shown as Inactive. 

When i highlighted the Timeslips add-in, its file location (shown below the available add-ins box) was blank.  I tried clicking the Add button, navigating to the Timeslips add-in application file in Program Files (...\Timeslips\TSOLAdllIn.dll) and clicking that to add, but Outlook said it wasn't a valid Office Add-in. 

Not sure what to try next. Any suggestions for a solution would be appreciated.