Akonadi not syncing one caldav calendar of many in same account

Greetings -

At some point a few months ago, Kalendar (and Merkuro) stopped displaying one of my webdav calendars. The calendar appears as one of my available calendars, but no events display, whether or not I select it

I’ve been using the same setup for years - same backend, same server, same login credentials - and other calendars hosted in the same caldav account still sync and display.

Thunderbird does not have this issue, nor does google calendar, or the calendar app I generally use on my phone (digical).

I ran akonadi console, and this calendar resource shows as having no items. If I manually try to synchronize the calendar, I get this error:

AgentBase(akonadi_davgroupware_resource_0): Unable to retrieve items: There was a problem with the request. Resource not found (404).

There’s lots more in akonadi console, but I’m not sure how to filter it appropriately.

Any suggestions on how to debug this issue? Thank you for any ideas.