washer would not spin out all of the water in spin cycle. installed a new belt , no better . now it siezed up
I assume it is still agitating. If not the problem is likely in the transmission if the motor is running and the belt is trying to turn.
If it is agitating then it is likely a problem with the brakes, but you can try replacing the thrust bearing, this part here. Also check the pump for an obstruction.
and see if that fixes things.