Trying to send Key Inputs - Uncaught Error: ERR 0x3401 in function "tap"

Ok, please can you try:

NRF.sendHIDReport([kb.MODIFY.LEFT_GUI,0,0,0,0,0,0,0], function() {
  NRF.sendHIDReport([kb.MODIFY.LEFT_GUI | kb.MODIFY.LEFT_ALT,0,0,0,0,0,0,0], function() {
    NRF.sendHIDReport([kb.MODIFY.LEFT_GUI | kb.MODIFY.LEFT_ALT,0,kb.KEY.A,0,0,0,0,0], function() {
      NRF.sendHIDReport([0,0,0,0,0,0,0,0], function() {
      });
    });
  });
});
// or...
NRF.sendHIDReport([kb.MODIFY.LEFT_GUI,0,0,0,0,0,0,0], function() {
  NRF.sendHIDReport([kb.MODIFY.LEFT_GUI,kb.MODIFY.LEFT_ALT,0,0,0,0,0,0], function() {
    NRF.sendHIDReport([kb.MODIFY.LEFT_GUI,kb.MODIFY.LEFT_ALT,kb.KEY.A,0,0,0,0,0], function() {
      NRF.sendHIDReport([0,0,0,0,0,0,0,0], function() {
      });
    });
  });
});

It's possible one of those will work?