@Kevin_Z 

i received my replacement unit 3 months ago and roughly around the same time i am in the exact same situation. my new replacement GX90 was working fine till 3 months last couple of days i am unable to connect to any 2.4 Ghz. SSID gets displayed when i try to connect to that connection doesnt get established. 5G1 and 5G2 works fine no issues there.

adding to the problem i bought a archer AX10 and was using it in AP mode . Upto a month it worked fine but after a month 2.4 has same connection issues but its 5G is working fine. i have completely different ssid's on 2.4 i use only 20 Mhz and use different channels in GX 90 and AX10 so there is no overlap.

i reached out support again afster the usual which suggested in my earlier post the option they suggested was RMA for another replacement. i told them it is odd the second GX90 is faulty but, even if that is the case what could impact AX10. so they assigned to a technical team and they asked me more or less the same information awaiting for a solution.

if SSID is visible and unable to connect seems odd and two different routers haveingthe same issue within 1 - 3 months seems off again. i really think there is something off which is triggerring this.

i am just exhausting options. any suggestions will be appreciated,