Check what security is set, and whether you have the 2.4GHz WiFi enabled still.
Some devices only work with thr 2.4GHz network not the 5GHz one. Having them both on and combined is ok, as is having them separate, but only having the 5GHz one enabled can cause issues.
Also, some devices, even those that are happy with 5GHz (such as my Sony TV!) fail if the security is WPA3. Change that to WPA2. You could try the combined WPA2-WPA3 one, but that sometimes doesn’t work either.