I have a new Deco X20 / AX1800 (US/2.6) 3-pack that I bought a few weeks ago on Prime Day. Our ISP is AT&T and we have the Fiber 1000 package (around 991Mbps actual into our gateway).

Today, AT&T came and replaced the original hardware with their newest BGW320-500, and leak tested the cabling from the dmarc in the street into the house. Our Deco mesh is set up this way:

1. AT&T BGW32-500 gateway (in IP Passthru mode, DHCP-fixed to Deco MAC address, internal wifi bands disabled)
2. Main Deco X20 (connected to BGW320-500 with Cat8 cable
3. Sat1 X20 about 20 feet away with no obstructions or walls between it and main, connected via wireless 2.4GHz
4. Sat2 X20 upstairs in a game room, approx. 80 linear feet with 3 interior (uninsulated) walls between it and main, connected via wireless 2.4GHz

We're still seeing speeds of only 10 - 40 Mbps from both satellite X20's (Win10 laptop w 300 Mbps link speed) and they're both only connecting via 2.4GHz to the main. The only way I can get the X20's to connect to the main via 5GHz is when they're literally right next to each other. When hardwired into port 2 on the Main X20, I can easily get speeds on my laptop over 600 Mbps (1.0GB link speed)

Any ideas why these can't seem to connect via 5GHz so the speeds can increase? I get Sat2 maybe being slower because of distance + obstructions, but the Main and Sat1 are literally in the same room (same height even). I feel if the Main and Sat1 would connect via 5.0GHz, the system would shift to Sat2 stringing to Sat1 at a higher rate of speed.

Edit to add: I've switched which X20 that I'm using as the Main to all 3, but none of them seem to be broadcasting a in 5.0GHz band (not to each other or to devices connected to the Main X20)