I have a pair of Bose Sleepbuds, which I exclusivly use when traveling. They are good at blocking out noise from hotel A/C units, elevators, people wandering up and down the hallways while having loud conversations, etc.
Unfortunatly they have a well known issue - the sleepbuds themselves get charged by a special charging case, and the battery management system (BMS) won't charge the battery in the case if it falls below a certain voltage. This means that, if you don't regularly chage the case (for exmaple because you are not traveling because of CoVID), the battery will drop below this voltage, and the BMS won't wake up and charge the battery.
This short writeup explains how to make them work again
Peel the bottom rubber cover off
This is simply held on with some doublesided adhesive. Warming it up will make it come off easier and allow you to more cleanly reuse the adhesive. Otherwise, just pull it and use new adhesive (or just leave it off and save a gram or two in your luggage!).
Next, remove the really small torx (or security torx, I cannot remember which) screws and pop the back off.
The root problem is that the BMS won't charge the battery once it falls below a certain voltage, so all we need to do is momentarily raise the voltage about that point.
Simply moentarily apply 3V across the battery - I used TP1 and Ground, and will soon update this post with better pictures showing where.
Note that the battery implies that it is 7V (7V 225mAh), but this is not the case, it is actually a standard 3.7V cell.
This at least got it working so that I could use them on a trip, but I'm planning on sometime extending these points so that thay are externally acessible, or repurposong the reset button to bridge from the USB input to the battery so that I can kick-start it with a paperclip.