Question Laptop issue: Runs off battery but not off AC adapter

Oct 21, 2019
Recently my sister came to me with an issue with her laptop:
For some reason, her laptop will not run off the ac adapter. It will only run off the battery. Oddly enough, the battery charges fine when the laptop is off but remains the only power source for the laptop when running. In Windows 10, no charger is indicated on the battery indicator icon. It only shows as running off the battery. Removing the battery shows that power is indeed going to the laptop as indicated by the light at the ac port but the laptop will not power on with just the ac adapter. It had no problems before today so I'm trying to find possible causes. I did check it with my own laptop's ac adapter (which is compatible with hers) and still the same issue.

Any clues as to what I could try to deduce the problem? Her laptop is an HP 15-af131dx, for reference.