Routers

Hi, first post here. I don't know much about routers or networks in general. I've been having trouble connecting to my 2.4GHz network and the only other choice is the 5GHz which doesn't work as well because range obviously. None of the devices can detect 2.4GHz and I don't know what to do. I've tried looking up solutions and trying to disable guest networks and whatnot but 2.4GHz simply does not appear in my wifi list. Using 5GHz is a pain because of speed and furthermore it disconnects and reconnects every 5 minutes. We have tried resetting the router multiple times and even factory reset today but it was all in vain. Can anyone help me out? Thanks.