Calendar not working on desktop browser.

I managed to get calendar working when using mailbox on my phone, but I can't create an event in my calendar from a desktop browser. I've tried Librewolf, Brave & Vivaldi. OS is windows 11.

I tried dragging iCal files onto the calendar, the screen responds as if it is accepting the file, but no event is created.

I also tried clicking on add to calendar button for zoom events, but get the the following error:

ErrorThe operation could not be completed due to insufficient permissions.

Any help on how to resolve would be appreciated.