It never makes it to the keypad routine. Unless you send something from the PC.
Then it only checks the keypad once.

Code:
Inicio:    <--------------------------------
 | USBService                               |
 |                                          |
 | contador = 1                             |
  ----> USBIn 3, Dados, contador, Inicio ---
  ...

  ...

@ READKEYPAD _Botao ' not working