Found that Wi-Fi private address feature in iOS 14 caused problems for me. After recent (2020-11) update to 14.2, Wi-Fi private address was enabled by default. This feature causes the phone to generate a new MAC address for each new wifi network it registers with. At home, we have 2.4 and 5 GHz bands, and the phone generated new MAC addresses for itself on both of these bands. So effectivity phone now has 3 MAC addresses at home: original non-private MAC, new private 2.4GHz MAC, new private 5Ghz MAC. I added these new MAC address into the "allowed" list on my router and all is good again. For anyone "locked out" of their network and unable to edit router access control list, simply disable the Wi-Fi Private Addresses feature and your phone should return to its original MAC address.