Hello,
I think you made a mistake about the serial number. Your son owns an Aspire R5-571TG-78G6 (NXGCFAA001.. instead of NXGCFA0016...). In this case, the best solution is to replace the full I/O board (inexpensive).
Here is the part needed:
| 55.GCCN5.001 | BOARD.I/O (power button soldered on this one) |