I'm experiencing an issue with my TP-Link Deco M9 Plus mesh network. Despite having multiple Deco units properly distributed throughout my home, all 20+ of my devices are only connecting to the main Deco unit rather than connecting to the nearest satellite units. My setup includes:

1. AT&T Fiber gateway in passthrough mode connected to the main Deco unit
2. Multiple Deco satellite units strategically placed throughout the house
3. Fast roaming feature is enabled
4. Internet connectivity works fine overall, but devices aren't utilizing the mesh properly
5. All deco units have strong signal.

What could be causing all my devices to connect only to the main Deco unit rather than connecting to the nearest mesh points?