No Calendar on iPhone

What I did
Tried to use Agenda on my iPhone

What happened
Calendar not working

What I expected:
Calendar to work

Things that might be helpful to know (Agenda version, OS and model, etc)
iPhone XR
iOS 16.6.1


Are these calendars visible in the native Calendar app on your iPhone?

Yes

Best Regards
Bruce Winter

Coincidentally the same thing just happened to me on my iPhone. When it happened I opened the native Calendar App, and scrolled around a bit. Then when I went back to Agenda, my Calendar appeared as normal.

Also be sure to update to version 18.1.1 which just went live on the AppStore, it contains a fix for people on iOS17 which can explain some of these issues.