Here are a few ideas for you.
I think 2 months is a while to go with zero gains in hanging (if you’re not getting at least 1/16” in a month with hanging, I think it implies a change is required). Maybe you should try a new angle and go back to doing 9x sets (if possible). I do think you should be able to make gains with far less than 9x sets, although if you have the privacy, you might as well go back to that since it was working for you in the past (try to replicate your success again). If you move to a new angle, a little maintenance at BTC is probably a good idea.
You could swap to OTS (over the shoulder) and work on wrapping the balls / stretching the bottom shaft skin (preventing turkeyneck). Eventually every has to work on this, and maybe now is a good time for you. If you haven’t maximized your suspensory ligament gains, you could go back to BTC / SD after spending at least a few months hanging OTS (guys have had success swapping between these angles; hobby called it the ‘seesaw effect’ theory).
If those angles stop working, you can experiment with other angles… UTL / OTL, or you can move on to fulcrums (e.g. RSDT).