Good; if Firefox shows the activities, then that helps narrow down what might be causing this. One other step to try to help narrow it down further, if you don’t mind. I think this might be related to the data we keep in the browser’s local storage. Could you clear your local storage in Safari, and see if that makes the problem go away? There are instructions for clearing local storage at https://www.laptopmag.com/articles/safari-delete-cookies, but make sure you DON’T follow step 3 which would remove local storage for all sites. We just want to clear the local storage for the languageforge.org site; to do that, you’d skip to step 5 in those instructions (click the Details button and delete just the local storage for languageforge.org).
BTW, deleting local storage won’t permanently delete any data. What we keep in the browser’s local storage is a copy of the project data, so that you can continue to work if your Internet connection goes offline. But it has sometimes happened that the data in local storage gets “stale”, especially after we deploy a feature to the website. I.e., what I think might have happened is that your local-storage copy of the project didn’t have the activity log loaded into it, and so whenever you loaded the page, the browser said, “Oh, I have this project’s data in local storage, I can skip downloading it”. (We do this so that people who are paying by the megabyte, such as people on cell phone data connections, will have a minimum of data used when they use the Language Forge site). Result: you don’t see activity, but in a different browser you do see activity.
So if you clear the local storage for Language Forge in Safari, and then you start seeing the activity feed show up in Safari, then that’s what the problem was. Please let us know if clearing the local storage fixes the issue for you in Safari!