Apple Calendar - Constant "The server responded with an error." messages

[MalagLagoon]

I'm running an old 2015 MacBook Pro and an old iPhone 7 Plus. So, perhaps the root problem is that I'm using old Apple hardware.

Today, radomly, I began getting these super annoying popup messages from Apple's calendar saying "The server responded with an error."

I'll get multiples of the same message at once; that is, I click "Try Again" or "Revert to Server, or "Ignore" and immediately I have the exact same message in my face - demanding my attention.

The sad thing is that I rely on my Apple calendar everyday. So, I can't really - just turn off my calendar and forget about it.

This problem reared its ugly head only this morning. So, at this point in time I've only tried rebooting my Apple machine. Interestingly, I haven't seen a similar problem with my iPhone 7 Plus.

I have a Google calendar, and a Microsoft Calendar connected to my MacBook Pro's calendar. Maybe randomly disconnecting one of the other calendars might help alleviate this problem?

Ideas anyone?

Is there anything I could check?

 

[MalagLagoon]

UPDATE: I believe the error has something to do with my Google Calendar. When I open Calendar on my MacBook Pro I see and exclamation mark next to the Google calendar email that I use.

 

[MalagLagoon]

Un-adding my Google calendar, then rebooting my Mac, and upon restarting re-adding my Google calendar - seems to be working.

I followed these instructions:

Calendar Not Working: The Server Responded With an Error, Fix • macReports

Several users have reported that Calendar is not working properly and they may receive an error message saying the server responded with an error when

macreports.com