In some cases, there might be a mechanical reason:
When the cuff is adjusted to the arm, the pins at the back of the plastic piece can be pulled out, and it cannot inflate anymore. You can try to push the 2 white pins into the strap of the cuff. Pushing them inside, might solve the issue.
If your cuff still does not inflate, please send us a detailed description, photos and/or videos, and the Serial number/Batch number to firstname.lastname@example.org. We will then open an internal investigation ticket and if it is defective we will replace it under warranty.