Ac3000 nighthawk x6s problems, just bought, please help

I just bought the ac3000 tri band wifi mesh extender, set it up and everything was working fine, I set it up to use the same name and password as my router, a linkysys max-stream ac5400. The problem is that if you sit in one place the connection is great and the speed is great, but if we move around the house, staying close to both the router and the extender, always having a strong signal, suddenly we have no internet, though we still show a strong connection, but no internet. The fix, to turn off the wifi be it in our android pixel phone, iphone X, or ipad, the fix is the same and works. How do I fix this problem? I am guessing this is a setting in either the router or extender, but I don't know what to do.