Cant connect to Synology RT2600ac

I think you’ve gone off topic. This is a connectivity issue not a performance one. I get decent to very good performance through out the house. I should have mentioned, I moved the 5G TMobile GW into the same room as the Synology router, not even 15 ft away and still the 5Ghz Wifi Band SSID did not show up in the prospective parent GW list