This is for a ZOOM event. Not tested to see if same thing happens with non-zoom events.
Steps I did
Create recurring event and leave "Capacity" blank.
- Set to register individuals only (to avoid Zoom problem with Group registration)
- Register button shows up on the event
Edit the recurring event parent and update children
After saving, the "Capacity" field is set to 0 (zero)
- Register button does NOT show up (unless we edit the capacity field to either blank or a positive number)
Workaround for Zoom meeting: Set capacity to a large number. Be sure to remember to update children too!
I think a zero or blank capacity should BOTH indicate "no limits" because it would never make sense to set the capacity to zero for an active event.