AC750 EX3100 won't allow device connections

For the third time: Mdel #3110 pruchased on 30-03-21 No firmware info with the new extender just out of the box.

My OS is Windows 10 Pro

OK - my current extender (Netgear WiFi Externder Model 2700) works fine, but I thought I might benefit from an upgrade. However after following ALL of the installation instructions to the letter and getting both my 5G and 2.4G connected from the router and recognized as connected I cannot get the new externder to connect to my mobile phone. I'm using the login for both 2.4G and 5G but no luck. I've tried rebooting everything. I've tried a factory reset of the extender (several times). I've tried using the login for my current extender. Nothing works. All of the lights on the extender are bright green and, according to my mobile phone, the reception is very strong. And I don't have this problem, or any problem with my extender using other devices, including my mobile phone.

When I try to log into my 2.4_2GEXT (WPA2-Personal) under password it reads (unchanged), The cannot connect error pops up if I try to login not putting in the password and also if I do use the password. Same with 5G.

I'll be reconnecting my current extender and using it to connect to the television in the bedroom below the room the extender is in and hoping for a solution so I don't have to return the extender to the retailer and try another brand.

Thanks in advance for any help.