Friend can't accept invite to the game

[juno.kyard]

I got deadlock back in august 2024 and invited my friend but he didn't accept it and now even though he can see the invite link on his email he can't get in, we've also tried http://store.steampowered.com/account/playtestinvites and https://store.steampowered.com/account/gatedaccess

Id be grateful if a dev were able to invite him
steam: https://steamcommunity.com/profiles/76561199574583555