Tamper lockout...how to fix it?

I'm reinstalling my Optima intruder alarm system. I powered it down, moved it then powered it back up with the remote LCD keypad like I normally do. It always seemed to work fine until now it keeps on saying that it's got a Tamper Lockout Fault on the screen. I've tried all the suggestions that I've found but they do not seem to work. Any ideas????