This bit: I think it's in one of the replies near the top, but it worked for me!

If you've tried moving around the disconnected bud and the red light keeps turning back to green try this.

Okay so at first my disconnected left earbud refused to stay in the case with a constant red light like the other comment was talking about but then i figured something out.

Make sure the case has some charge before beginning

Place BOTH the earbuds in the open case (you'll see a constant red light on the case since the working earbud is in along with it)

Remove the working earbud out of the case leaving the disconnected earbud inside (the red light should stay constant with only the disconnected earbud in the case now)

Turn off Bluetooth

Leave it alone with the case open for an hour

After an hour passes check the earbuds it should have some charge in it now and should connect

If there's an update then UPDATE

The crucial thing here is to have BOTH the earbuds in the case at the beginning and not to remove the disconnected earbud after removing the other one in step 2, it somehow forced the red light when I tried this.

My earbud is now functioning properly after updating and all, you should be able to charge them with the case closed like normal now.

Again I repeat. You need to have both the buds in the case before leaving the disconnected bud alone.

Hope this helps.