Second tv is a problem.

We have two TVs connected to our decoder, the main tv is fine, the second, however, isn’t.

At first, it said “weak or no signal” then we reconnected the wires hoping that this would solve the problem, but then it said “source not connected” and the HDMI option remains unhighlighted. I have swapped cables to make sure the second tv’s cable works, and it worked without a hitch on the first tv. Please advise.