The problem is that somehow, all members in the forum are now set to the Administrative usergroup, and all secondary usergroups are cleared. I have not been able to find the link between aMember and XenForo that would change those groups, especially when someone pays for a subscription (gain access to forum), or a subscription expires (lose access to forum).
For damage control, however, we want to restore the usergroups back to at least the Registered usergroup so members can get back in normally; we will iron out the subscription issue afterward. I understand that XF doesn't have a mass usergroup change feature, but what else can I try? I have a couple of ideas:
1) Is there an add-on? I had no luck searching for one.
2) Would usergroup promotions work, even for one-time use?
3) How about a database query? I don't know which tables need to be touched to make certain the correct usergroups get assigned.