Setting up MoCA

I purchased a roamio pro and a mini. I have the roamio connected and working but when I try to set up the mini it says it can't connect. All I need to do is have the roamio connected to my router and then plug the mini into the coax right? I have the main cable line split using a splitter of course and then one line from the splitter to the roamio and the mini. What am I doing wrong?

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