I discovered the issue was due to upgrading The Events Calendar. Deactivating TEC solved the issue.
Updating to 5.1.9.1 wiped out fields from appearing on edit screens in the backend.
The settings for each set of fields were wiped out “Show on … custom page type”. I added that setting back, but nothing changed.
I can select the ACF fields in the “Show on screen” settings and that seems to fix the issue.
The data still exists since it is showing on the frontend.
This reply has been marked as private.