DIAGNOSIS The 6GHz band is often hidden by default or has separate settings. Your phone might also be defaulting to an older band for compatibility. The most common culprit is the "6GHz Shared" or "Dedicated Backhaul" setting on the Orbi.
FIX First, in the Orbi app, tap Menu > Advanced > Advanced Wireless. Look for 6GHz Settings. Ensure the 6GHz WiFi is set to "On" and the 6GHz SSID is set to "Shared" or "Separate SSID," NOT "Dedicated Backhaul." If it was on Dedicated Backhaul, only the satellites use it to talk to the router—your devices can't see it. Change it to "Shared," save, and reboot your system. Your 6GHz network (usually YourNetwork_6G) should now appear.
IF THAT DIDN'T WORK On your phone, go into WiFi settings and look for an option like "WiFi 6E mode" or "Enable 6GHz band." On some Samsung phones, it's buried in the developer options. Also, make sure your phone's software is fully updated, as early WiFi 6E support had bugs.
HEADS UP The 6GHz signal has much shorter range and poorer wall penetration than 5GHz or 2.4GHz. You'll likely only see and use it when you're in the same room as the router or a satellite. Don't expect whole-home coverage on the 6GHz band.