Keep getting errors when using my Calendar

[ToddJ]

Whenever I try to use the Calendar app on MacOS Mojave, I keep getting a "the server responded with an error" and "The URL https://p50-caldav.icloud.com/1044137595/principal/ encountered HTTP error 404. Make sure the URL is correct." What might be causing this?

 

[ToddJ]

It seems to be getting worse

 

[desertman]

I don't know what causes this. However, I have had weird error messages with Calendar myself and could resolved them by logging out of iCloud on all of my devices and then logging in again, one by one. This might not help you, but it is easily done and could be worth a try.