no longer recgnizes a usb otg drive

[konakona]

In-app usb otg detection used to work fine for years. Just recently though, I started having a situation where a usb drive otherwise recognized everywhere (other media players, file managers, android notification, etc) is not seen in GMMP and GMMP only. 

When editing the scanner scan path, /storage is empty and I can't move up any further in the directory hierarchy level. Local (built-in sdcard) media resides in /storage/Music and that works without an issue.

GMMP does have storage permission, which specifically mentions accessing USB media. I have a vague suspicion that the permission somehow got a bit wonky, so  was trying to disable-then-reenable at no avail (says I need to first disable the draw over other apps permission, which is greyed out for me).

What else could we try here?

The OS is rooted MM with a custom (timur's) kernel btw.

[konakona]

Solved! apparently this is not entirely GMMP issue, per se, just confused because some 5-6 other apps I am using are unaffected. Also, GMMP had no issues with USB media on the same OS for years which is why I was puzzled.
Anyway, all you have to do is do the following in a terminal emulator:
su
sm set-force-adopatble true

[GoneMAD]

gmmp only reads usb media that mounts to the local file system. if its not mounted correctly it will not be visible to gmmp

[GoneMAD]

also the scanner lets you manually add paths. There should be a toolbar icon that is a folder with a plus sign on it. Click that and manually add the path. The pop up folder selector is limited by what the OS returns when traversing the file system. Access to the parent of /storage is denied on most newer versions of android