Motorola modem mb8611 no cable tv through coax.

I have a Motorola MB8611 modem connected, and internet is just fine. My wireless flex box works just fine too. I have a  DVR set top box and have connected it to coax at a powered splitter (I have tried non-powered, too), and I am not getting a signal. I get the error RDK-03036 error. Any suggestions? I have tightened and retightened - switched ports on the amplifier/splitter. No luck. I have upgraded from flex as well.