Hi Morgane,
I am having trouble as well. I wasn't able to register for my exam myself as I was getting an error the minute I click the PSI link from CLARB's website. But, I received a call back from PSI to schedule my exam a few days after continuously following up with CLARB. My account still hasn't been fixed and this has been going on since April.
CLARB is the only way, I've noticed they answer calls first half of the day for some reason. Hope that helps.
-Rutusha