WiFi Router Won't Connect ro RV

I have Spectrum WiFi using a arris modem and sagemcom router provided by spectrum. I have a large brick home and the signal must pass through several walls. I have tried to get the WiFi signal to my RV next to my residence. Where the cable comes into the house I put a splitter before going in to go to my RV and hooked up a netgear nighthawk router. The signal shows great , but it won’t let me access it. What is wrong?