Apple Watch Series 2 won't charge

Bought it used a year or two ago.

It worked fine until a few months ago when it stopped charging.

I assumed that the battery had just gone bad.

Bought a new one, installed it, and it still won't charge.

So either the new battery is faulty or something else is wrong with the watch (either from age or from when I opened it up).

It is probably not possible to troubleshoot any further, or not cost-effective as the part that is probably bad would cost more to replace than the watch is worth.

Thoughts?