I have a gig fiber connection.  When the pandemic hit, and my wife and I were going to be working from  home, we upgraded to the Archer . Prior to December 2020, I was getting 700-900 Mbps up and down.  Then in January, my upload speeds dropped to less than 100 Mbps, generally 50-60 Mbps. This was when I was using the speedtest function of the router itself, not from a PC directly. I didn't pursue this at the time, because we were house hunting.  Now, we're in new house.  New fiber connection (Same provider).  Same Archer AX6000, same speeds.  Using the Eero mesh router provided by the ISP (Metronet), I get 8-900 Mbps symmetrical.  Using an old Nighthawk router, I get 8-900 symmetrical.  Using my AX 6000, I get 700+ down, 54-60 up.  

I got the AX6000 because I wanted to take advantage of my upgraded WiFi cards (yes, both my wife and I have PC's with WiFi 6).  Now, I can't even get DSL speeds using this.  Is there a solution?  My QOS was set to standard, and in fact, I even factory defaulted the router today and I am still getting these same speeds.

Any assistance is appreciated.