Unable to connect older devices [Edit]

I solved my problem. I previously named the new modems wifi different than my previous 2.4 ghz wifi. So my devides were looking for a wifi that didn't exist. Giving that the new name was attributed to a 5 ghz wifi caused a double problem. So I left that name as it was and added a new wifi network with the old name and attached it to the 2.4 "output" of the wifi. It worked. If the device worked after the change, then fine. I then set each device to the network that it connected to. So the router must be a two ghz, 2.4 and 5 ghz. It was a matter of seeing which network name worked with the camera, or thermostat or whatever. So, I consider that a success. worth a try.