Yamaha DXR12 Powered Speaker, protection light on

Hello, I had the protection light staying on and found 2 of the 4 mosfets were bad so I changed all four mosfets (3603) on the amp circuit board. This is my problem, when powering up, the power and protection lights come on and after a few seconds the protection light goes off and speaker works, however if I turn the unit off and back on the protection light stays on and speaker doesn't work. Now if you leave it off for 30 minutes and then power the unit up it works again. Where should I be looking to correct this problem? Thanks for any help with my problem!!