Internet Advancement Issue - Adding Activity and Attendees

Sounds like it’s probably the same underlying issue as this report: Can't edit Camping in Activity Logs

Per SUAC on that thread, the developers are looking into it on Monday. I would keep an eye on the change logs for IA2 to see when the fix hits.

Once it does, based on my experience, you’ll probably need to do a forced reload of the page to see the change.