@itsharman have you tried another cable yet?
I used to work in second hand console and this was a very common problem with cheap £1 cables and third party pads. (The official PS4 cable is like £5 at GAME).
If you have tried better data capable cables, and the pads are legit DualShock 4’s and still nothing happened could it be the USB sockets are fried?
If not the cable: have you tried another HDD yet?