Troubleshooting

We had to restart

Sorry, we had to restart because this add-in wasn't responding  

Running a synchronous operation for more than 5 seconds will cause this error.
The add-in may have exceeded the run-time resource limit for an add-in.

link - learn.microsoft.com/en-us/office/dev/add-ins/concepts/resource-limits-and-performance-optimization 
link - learn.microsoft.com/en-us/office/client-developer/shared/troubleshooting-office-files-and-custom-solutions-with-the-telemetry-log 

To prevent the error from occurring, you should change the registry value in Excel.
This will turn of resource limit checks for the add-in.
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\16.0\Wef] "AlertInterval"=dword:00000000
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Wef] "AlertInterval"=dword:00000000

App error: Catalog could not be reached

Check the firewall settings because Catalog refers to the Office store.
Unable to access the Office Store

This add-in seems to be having problems

This add-in seems to be having problems 
Click "Restart" to try starting it again