WiFi not working

My iphone shows connected to my network and my ethernet devices work.  But apps on my phone and wireless devices in my home are not.  I was originally installed with the XB7 about a month ago when I switched from Astound to Xfinity.  I had problems from the beginning as described so Xfinity exchanged the XB7 and installed a EXR10.  No difference - constant on/off.  So before I give up entirely on Xfinity I want to try my own router.  I will keep the black box PON.  I don't want to connect to the EXR10 if I can avoid it.  I was considering the TP-Link Archer AX73 router.  Thoughts?  If this will work, do I need to have xfinity do anything to allow my router?  Thank to any insight.  MJC