XPS15 (L501X) Won’t Charge

Hi, I have an XPS15 (L501X) that I’ve not used in years, but want to start up again.

I got it out and tried, but the battery was dead and when I plugged the power lead in the blue light at the end of the cable dimmed and went out.

I bought a new (non-OEM) battery, attached it and (important info) the laptop started up on the partially charged battery and I even logged in - all before the battery died (within a couple of mins). The laptop would still not charge however, and I’ve had a range of flashing light sequences. 3 orange, 1 white. 1 orange, 1 white. 1 long white, 1 short white.

I ordered a replacement power jack/port, fitted it and no improvement.

I bought a replacement motherboard (also came with CPU) and again, still no improvement. I now still experience a flashing light sequence of 3 orange, 1 white.

The only thing I haven’t done is bought a replacement charging cable, but the blue light at the end works so I’m inclined to think the charger is fine?

Losing my mind, and money, trying to fix this thing! Any help would be hugely appreciated!