You pointed out you had it turned up to max without it helping. I think the problem is that you didn't research the correct use of the device to get a good understanding of how to use it. No offense intended here. I will copy my earlier post here in case you missed it.

TENS, my friend is how to get immediate and real relief without drugs. They are portable controlled electronic devices with remotes, have two channels (one for two different body treatment locations; both locations can be treated at the same time), can be worn beneath your clothes, slept with, and go about your business with. They also work on a timer, some have selectable timers. The majority are USB rechargeable; no batteries to change. The transducers are reusable if you protect the adhesive surface when not in use. You need to spend (Amazon or eBay) less than $100 to get a good one. It isn't a cure but a sure relief. I suggest you research it on Google. Also Google acupuncture, acupressure, and dermatome charts. A quick tip; get the transducer pads between the spinal nerve root serving the offending nerve ending. Set the current to the point where you are certain you feel it and then back off to one lower-down setting, use it there. A high current setting will cause muscle soreness, due to the pulses that contract the muscles, the higher the current the greater the contraction; you neither want nor need that.
There is a wealth of info to be found on Google for how to use them. Many nights I would get no sleep if I didn't have mine next to the bed available for use.
I know of no other side effects; Check with your doctor before using if you have a pacemaker or other implanted electronic devices.

I guess we’ll just keep trucking as they say!
Hopefully we’ll find something to help one day!