Why doesn't my G30 Control Box fit in the bracket? 

If your control box is not sitting correctly on the boiler, the lugs need to be moved into the row below.

This will raise up the Connect Control Box and it will sit in place. The box is held firmly in place by the lugs, then it sits on to the metal bracket, not in it.

The bracket is there to protect the wires underneath the control box. The lugs have two rows so the control box can fit the Original Grainfather as well as the Bluetooth Connect Grainfather.

Please unscrew and move them down one and this will solve this issue. Refer to the page below, found in the instruction manual for more detail.