Occasionally, the food tray may become misaligned from the rotating tray mount underneath it, especially if any kibble gets in its path. When this happens, you may notice that the tray mount (or food tray and tray mount together) is stuck under the Hub's motor, making it difficult to reattach the tray. This can be fixed with a few simple steps:

Press the dome switch for a few seconds. This is the small rectangular slot at the back of your Hub, where the dome would typically snap into place.

Release the dome switch, which will cause the tray mount (or the food tray and food mount together) to swivel out. 

If the tray mount still doesn't come forward on its own, try gently pulling it forward to the open position while still pressing down on the dome switch.

Lightly place the tray over the tray mount.

Press the dome switch again, causing the food tray to retract and realign with the tray mount.

Note: while the tray itself can be removed from the Hub, the swiveling tray mount was not designed to be detached from the Hub, and removing it may cause permanent damage.