Many products, like Ring Cameras, Irrigation Controllers, Water and Power Meters all strictly use 2.4Ghz Wi-Fi, not because it's old tech, but because it's the better frequency choice for longest range.
5Ghz is much faster, but has much shorter range. These products don't need speed, they need signal strength to reach their more remote home locations.
Be careful what you ask for.
I had a mesh point 5 feet away from my Traeger and it would not connect on a 2.4 network. So, I upgraded to the widest range available....my neighbor across the street gets a full strength 100mb/s download speed on my network. Still nothing.
Are you sure it is the WiFIRE Controller not connecting to your 2.4GHz Radio and not the App Device defaulting/switching to its preferred radio (i.e. 5GHz) during the setup process? That being said, depending on who's Mesh Network product you are using, you may find it necessary to disable the 5GHz radio long enough to run through setup and complete, and then you can re-enable the 5GHz radio ...