5 gHz wifi doesn't show up in list of available networks

In order to set up my new printer it was necessary to have a separate 2.4 gHz wifi. At first, both names showed up on the list of available networks, but now only the 2.4 gHz name shows up. Resetting the modem has no effect. Tech support claimed it was my devices. I contacted support for the devices and they tried everything they could with no effect.