Mesh point 2.4G SSID works, but not 5G?

I have temporarily moved into my parents house and brought my Amplifi mesh point, which has worked well in my house for the last 5 years. They have a standard router from their network company (HG695b router).

The mesh point receives 5G as the backbone (app says good signal range) and I have set up both 2.4G and 5G SSID's, so I can easily see what to connect to. When I look at the list of available wifi connections on my devices, I can only see the 2.4G SSID, no matter what I do in the app.

I have tried factory reset (via the app) and moving the mesh point around, but it just doesn't want to broadcast the 5G. I don't have the options available on the app for a 'hidden network' or anything like that. Any suggestions would be much appreciated!!