(PS4 Pro, EU)
Since Trove Heros update, you couldn't send someone an invitation. But since a few days later now you can invite someone and the invited player will get the invitation but he cannot accept the invitation and join you. After you clicked 'join' you just get back to the game and nothing happens.
All players suffer from not being able to invite and get invited. Instead, we have to join the player by club, a party or the friend list. I hope this report will help you to fix the problem.