Hi @kevlew,
Please read this support topic:
Also, I'd suggest you deactivate all antispam plugins and check again.
@sofy, that support topic is not relevant to our situation. These were posts made by users with usernames and they are no longer displaying correctly. They show as anonymous despite being made by legit users.
seems like wpforo is only showing user names for any post that happened 6 years ago.......all after that are anonymous and not being counted.
I don't think wpForo has any problem here. If wpForo can't show users data and dates then you have problem with database data. Your database is crashed or you've made some incorrect manipulation with users data. This needs to be investigating in database. If you have a backup file, just restore it.

