If your WiFi 6E devices are not connecting to 6GHz, this may be due to your device(s) software being out of date. Ensure your devices are updated to the latest available software version (i.e., Android OS, etc).
If your device is still not connecting to 6GHz after updating to the latest software version, try enabling Wi-Fi Protected Access 3 (WPA3). For instructions on how to determine if a device is using WPA3 and how to enable WPA3 on your device, refer to What is WPA3?
Note: Some legacy devices may not be able to connect with WPA3 enabled.