Not all computers and wifi capable devices are capable of operating on 5 ghz networks. If your device is a little older or was a budget item amd can’t stay connected to the 2.4 ghz networks, it’s not the fault of the router (which is obvious if you have other devices that can connect with no issue). Just buy a capable usb wifi dongle.
https://www.amazon.com/NETGEAR-AC797-100NAS-Download-Anywhere-Unlocked/dp/B0866TKPMS

