EX6150 No Longer Working Correctly with Sagemcom RAC2V1S Router

I live in Western NC. My internet is through Spectrum. The router they provided is a Sagemcom RAC2V1S.  Because of the odd layout of the house, I bought an EX6150v2 about a month ago. It worked splendidly until two days ago.

Since then, if I connect to the extender network, I can only get response from major websites like google/gmail and facebook.  Attempting to get to nearly anything else times out (even ESPN.com).  If I log on to the regular router wifi, I can get to everything.  I've looked around trying to find what is causing this and there is some thought it might be a MAC problem.

Unfortunately, I have a liberal arts degree so that's a bit above me trying to figure it out. Anyone know of a fix they can explain to a dummy?