Custom Transparency Mode Keeps Turning Off SOLUTION
Guys, i just find out the solution to this problem, but i really canno get why apple do not share this to community earlier, cuz its not bug, but function "headphone accomodations" that turned off straight on apple watches by default :(
So :
1.make sure that watches not connected to iphone (turn off bluetooth on iphone settings)
2.plug in your airpods, and try to play some track (to make sure that pods directly connected to watches)
3.then if track started playing in your airpods from watches source, press main button on watches, and list down to Hearing settings (ear button), also list down and turn on the Headphone Accomodations, this will turn custom headphones settings (including transparency mode settings) directly on watches
4.Voila! You can turn on bluetooth again to pair back with yo iphone