My friend rejected the invitation as a joke and now is locked out of the game

[airjairj]

My friend is a moron, he rejected the invite, and now he shows as "pending" on my game, and while other friend can invite him, their invites dont show up.
We tried the link https://store.steampowered.com/account/playtestinvites (nothing here).
Can anyone help please? Here is the moron's steam profile (profile link)