I’m not a computer geek, but here are a couple things that I’ve run into regarding this:
Do you wait a few seconds? Mine (macbook pro) takes a few seconds to go from “not charging” to “charging”. Second, you could check to see if the connection is faulty. That is, does the cable need to be moved around a bit?

You may also need a new battery.

Is there a battery maintenance feature that can be set to stop charging at a certain %? My Lenovo does. For mine, optimal is 50%, but I can set it to 5% if I want. Maybe yours has something similar, and became set to a low %.

Keeping a battery at a low charge is harmful to the battery. Always best to keep them at 100%.

Li-ion batteries will crap out if kept at 0%, but degrade in 2 years if kept at 100%. Longest life if kept at 50%, but that is inconvenient if you are out and about all the time.