I still haven't figured out why do the game (GTASA) is not accepting the keystrokes, though it can really recognize some of the strokes.

I wrote my own 'print' method to put each key, then a zero but not worked. Then I've inserted a delay between keystrokes, and yet is not working. Even tried to send several zeros in between each keystroke but still no success.

void my_DigiKeyboard_print ( char *str ) {
  uint8_t data;
  
  while (*str) {
    data = pgm_read_byte_near(ascii_to_scan_code_table + (*str++ - 8));
    DigiKeyboard.sendKeyStroke(data & 0b01111111, data >> 7 ? MOD_SHIFT_RIGHT : 0); 
    DigiKeyboard.sendKeyStroke(0);
    DigiKeyboard.sendKeyStroke(0);
    DigiKeyboard.sendKeyStroke(0);    
    DigiKeyboard.delay(100);   
  }  
}

In any other application the keys are correctly injected, it is weird.. I still have more work to do.