(Redirected) Inspiron 3552 Charging / Battery issue

I've had an issue for a couple of weeks now where my battery wouldn't charge, but the laptop would work when plugged into the AC power supply. I picked up a new Dell battery today.

With the battery in, and no AC power supply, I get the following BIOS message: WARNING: The battery is not recommended for this system, the system will be unable to charge this battery. It boots up ok afterwards. When I plug in the power supply, the power icon in the start bar goes from Battery - xx% to Plugged in - not charging.

On battery only, going back in to BIOS settings, specifically Battery Health, I can see the message 'This battery is performing normally'.

With the AC power source connected, and the battery in, I get the following BIOS message on boot up: The AC power adapter wattage and type cannot be determined. The battery may not charge. Please connect a Dell 45W AC adaptor or greater for the best system performance. WARNING: The battery is not recommended for this system, the system will be unable to charge this battery.

Going straight in BIOS on AC power, and under AC Adapter Type it says 'Unknown'.

Booting through to Windows 10, I can see the battery icon in the tray, saying xx% available (plugged in, not charging).

I have measured the external power supply voltage at 19.6V DC.

As I have issues both with and without the AC power supply, does anyone have any ideas what the issue is?