The Location field is only for network calendars, not the Home calendar which is defined on the local computer, in the profile folder. Location is the CalDAV URL and is defined by the calendar provider. With e.g. Google calendars, it is set automatically at calendar setup.

Thank you for the reply. When I checked the properties of the Home Calendar it came up as "file:///C:/Users/CWC/Dropbox/Home.ics". I would like to have it in my profile. Is there guidance somewhere on how to do that? Can I just import the Home.ics file to thunderbird using tools>import? Are there risks in doing the import? Will I need to change the location in properties or will that be automatic?

I think you can just import the ics file, but I would rename it to something like Home2.ics, just to keep it separate. If it works, you can delete the current Home calendar. The calendar-data subfolder of the profile stores calendars.

I tried to import a couple of times. The first time I imported the Home2.ics it failed and suggested I try importing as a .zip file so I tried that and it failed also. The file is 1005 kb in size. The error console looked like this (which means nothing to me):-) tb.account.size_on_disk - Truncating float/double number. 2 tb.account.size_on_disk - Attempted to set the scalar to an incompatible value.

A quick web search about import errors gives many results, none of which may help, e.g. try opening the ics in a text editor and remove any entries with "LAST-MODIFIED":

https://support.mozilla.org/gl/questions/1418803

It shouldn't make any difference, but try importing from the Calendar tab, Events & Tasks, Import...

Thanks for trying to help. Nothing worked and I've decided to abandon the project.