Did you try the "Change Wi-fi network" setting under Device Health? That will resetup the wifi.
You can also try to reset or resetup the device.
Lets try and get one thing straight here, regardless of your router broadcasting seperate or both radio frequencies together makes no difference (unless you have any leagacy products which may struggle) to the connection as these cameras etc. are able to distingish which radio frequency to connect to (just like any other products you have that only use specific radio frequency be is 5ghz or 2.4ghz the devices are able to distingsh between them).
I have tried a router / access point / extender / Mesh all within 2ft of a Camera (both wired and battery) the camera finds the right frequency (have tried broadcasting both on same SSID, just 2.4ghz on one SSID and even created new seperate SSID) to connect to (has even found nieghbours) it connects and all seems fine but always finds the wifi signal being weak! i get weak signal errors when wacthing live view etc.
Just like with many of the Ring products they have seriously cut corners on the hardware/firmware.
This just my view from what i have gone through and faced, but a lot of my issues sound quite familiar to a lot of others on this community.