How to install a XiD-P box for a second tv.

The main box is a XG1v4-A and is fed from a splitter that is fed from the main cable coming into the house.  Out of that splitter is feeding the internet modem and a second splitter whose output feeds both the XG1v4-A and XiD-P boxes.  The internet and the XG1v4-A box work just fine, but the XiD-P will not connect.  I keep getting error messages telling me to tighten connects.  Believe me when I say ALL connections are tight!  When I started having problems I contacted tech support and followed their recommendation to exchange cable boxes.  Then after hooking up everything as it was previously installed nothing worked.  Further trouble shooting identified one bad splitter and went to Xfinity store and got two new splitters and hooked up all cables as previously installed and the XiD-P box will not hook up. I even swapped the coax for the two tvs on the splitter and still got the same result.  Through all this, the internet works fine.  Is there some unique step to getting the XiD-P to work or is it bad?  Thanks for your help.