The status of this response is Pending and require some modification by the author.
I have a Honor 4x che2_l11. Before upgrading its firmware from 4.4.2 to 6.0.1 it could easily recognize a sub flash drive connected to its sub port , but after upgrading it can not ,
So I think it should be a software problem not hardware.
I upgraded it to connect it to the car stereo , now I can change tracks via my car stereo , but the sound is not played in my car stereo.