I reached out to the team handling support during the beta phase. We should have invites regenerated for you folks “soon,” but new invitees shouldn’t experience this problem as they will be added to the repo directly/automatically, without having to accept the invite.
For the suggestion to open a ticket with our direct Support team, it might not be possible. Free-tier users who may have invites, would only have access to our forum here. So for this case, I reached out directly and we should be following up.
So hopefully those expired invitees will need to have it re-generated, and opening a ticket with Support is a good option.
If you are a free-tier user and have an expired invitation, please @ me here.