What band is the remote set to? Check by pressing the system info button on the front of the receiver. They need to be on the same address, and band to work together. For the 21.0, Band A is odd numbers, and Band B is even numbers. The 6.3 has a switch next to the batteries that determines the band.
To change the remote address, hold SAT on the remote, press any number 1-15 on the keypad, press #, and then press record a couple times.
*EDIT* gtal98 beat me to it. Go with his suggestion
To change the remote address, hold SAT on the remote, press any number 1-15 on the keypad, press #, and then press record a couple times.
*EDIT* gtal98 beat me to it. Go with his suggestion