Thanks - this worked for me (QN95/Q930C WIFI pairing failing on different bandwidths).
Given that routers (particularly those supplied by ISPs) are commonly being shipped as both 2.4GHz and 5GHz capable but defaulted to using the same SSID, it's surprising that Samsung have not done something about this over the last year since the original post. It feels like a relatively straight forward software update on dual-band capable devices (and the SmartThings app) would allow for an additional network settings option to select between (a) Both Bands - default, (b) Just the 2.4GHz band, or (c) Just the 5GHz band. This would allow the problem to be diagnosed and fixed from the devices themselves rather than palming it off as a router-issue (which have vastly differing steps to resolve this, and some 3rd party routers are even locked from changing these settings). In addition if the Auto-Fix option from the diagnostics was to attempt resolving this known issue of different bandwidths, then this would also have fixed the problem.
I have found the interfaces and range of settings on my Samsung devices to be quite good and the interoperability to be great, so am sure this is just an oversight - after all 5GHz Wifi has only been around since 1999 (though it only hit 68% saturation in 2015 according to the Wi-Fi Alliance/ABI Research report).
Edit: I had a similar issue on my S22 phone connecting to 2.4GHz only 3rd-Party devices (which the apps now work fine, but during setup they needed to be on the same band), and there appears to be no way to tell the phone to temporarily just use the 2.4GHz band... By changing to 2x distinct SSIDs this also solves that problem, but I now lose the automatic selection of 5GHz when available for better speeds.
Hopefully Samsung reps monitor these community suggestions and can pass this suggestion on, and we can get a robust fix.
