Thereagun Mini (2022) Dead Battery?

My wife has a Theragun Mini from 2022 that no longer turns on and/or holds a charge. So of course, I came to iFixit for the teardown and I was sad to see there wasn't one.

Does anyone have a repair or tear-down guide for the 2022 what I guess is the original Theragun mini?

I found this video here which showed the result of cracking open the case. However, it doesn't show him putting it back together. HA!) You can hear him describe his theory as to the battery type possibly being three Panasonic 3400mAh batteries run in series (based on the tennis ball yellow/green color). He later reads a part number "31NR19/66" which unfortunately come in a range of sizes. And finally, he mentions that "they look like 18650s to me" which seem like a technical form factor.

While I'm not surprised that a 4 year old electronics product has died, I am very disappointed in Therabody for designing a product so aggressively anti-serviceable by an owner or third party.

Any advice or help would be greatly appreciated. Thanks.