Can't play trial on PS4

My brother played the trial version on PC a couple years ago, but ended up not getting the game at that point. Recently, with the unlocking/expansion of the trial version, he wanted to try it out on PS4. However, when he tries to login, he gets a message "there's is already a service account" or something to that effect, and he's not allowed in the trial.

Can anyone help on what's going on and how to get into the trial?

Trial isn't cross-platform. A trial started on a PC can only be played on a PC. To play on a PS4, you will need a new trial account or buy the game on PS4.

By new trial account, do you mean to make a whole new service account or is there some way to add a PS4 trial to an existing one?