My brother was sent an invite on the 23rd, and they said they have not received the actual invite notification yet. They previously played the game using family share, but currently cannot open the game after the family share was revoked.
Description:
When inviting another user in your steam family to the deadlock playtest if that user then plays a family shared copy of the playtest the title's in game invite menu marks them as having "Already Joined" despite them not receiving or accepting an email invitation. The invited player is then still marked as not having access within steam and is shown a blue "Purchase" button on the game in the library tab of steam.
Note:
Having both accounts change their steam beta participation to none does not appear to impact or workaround this issue.
Repro Setup:...
devs said they are working on it, as per:
apologies to hear about this. i hope your brother can get his invite soon