Are all invitations for regional qualifiers sent out? How and when do we know if we made it into regional based on skills?
Look for invitations on the next business day after the last event in your region (or shortly thereafter.)
You can do a search at robotevents for your region, competition and grade level to see if your rank is high enough to be invited.
It is quite common for all the registered teams to be in the top of the skills list. This means that if your event has spaces left and if your skills rank is at or lower than the capacity of the event, you would likely get an invite.