When I try and log on to the forums with another account it shows the message with blue letters
Either the site is offline or an unhandled error occurred. We apologize and have logged the error. Please try your request again or if you know who your site administrator is let them know too.
but i can log on to GrandChase's forum just fine. Just not Trickster's.
Avatar by IrRandom
Try send a 1:1 support Ticket about the issue from the account that have the issue. If its an account side issue(which seem likely), contacting them from that account, makes it easier for them to pinpoint it. ^^