Diagnosis
WiFi 6 (AX) can be faster close up, but its higher-frequency signals (especially on 5GHz) are often worse at penetrating walls and obstacles than older standards if not configured well.
How to Fix It
Log into the web interface. Go to Wireless > Advanced Settings. For the 2.4GHz band (which is better for range), set the 'Wireless Mode' to 802.11 b/g/n/ax mixed. For the 5GHz band, ensure the 'Channel Width' is set to 20/40/80 MHz (not 160 MHz). 160 MHz uses more channels but is far more susceptible to interference and range loss.
If That Didn't Work
Try repositioning the router. The internal antennas are omnidirectional, so vertical placement (standing upright) in a central, elevated location, away from large metal objects, appliances, and other electronics, makes a huge difference.
Heads Up
The 'Smart Connect' feature can sometimes steer a device to the faster 5GHz band even when the signal is weak, causing dropouts. Splitting the bands into separate SSIDs and connecting range-challenged devices to the 2.4GHz network manually is often more reliable.