Sorry to hear that. If you just bought your Max, you certainly should be able to return it to the store you bought it from for a new one, but here are the instructions in any case:
If you look at the encoder, there is a cap on top, the inner most circle, which you should be able to gently pop out with a pick or similar type of tool.
You should now see the nut. Gently loosen the nut
Lift the encoder knob at the sides and make the nut level with the top of the shaft.
Then tighten the nut without the letting the sides drop down.
It’s important that the nut is level with the top of the shaft. That will allow it to have the push function and to make the popping noise.