RE: XPS 18 Tablet not charging while plugged in??
When charging works when the laptop is off but not when on, the problem is usually the charger itself - not enough watts to do both. First thing to do is acquire the next higher power charger. This usually does the trick. Usually a replacement charger at the same wattage could fix it, but the higher power supply is best. Several years ago, Dell sold a laptop that just wouldn't charge while running for many owners; the answer was the higher power charger.
XPS M1530, Win 10 CU Pro 32-bit
Inspiron E1705, Win 10 CU Pro 32-bit
Dimension 9100, Win 10 AU Pro 32 bit
Inspiron 660, Win 10 CU 64 bit
Inspiron 3668, Win 10 CU 64 bit
Asus T100 Tablet, Windows 10 CU 32 bit