The only thing I can offer at this time is that if all the requirements for sub detection are being met (Season xx Folders, proper naming and identification techniques employed) external subs are being recognized across the board in all apps (at my disposal):
I ran those ‘Godfather’ externals in as a test just now - I have many, but couldn’t find one/remember where - on short notice.
You will absolutely need to reveal which client/device you are having trouble with - or mention if it’s all/any.
You will also need to have Local Media Assets enabled under ALL Tabs for ALL Agents at ‘Settings/Agents’. It does NOT need to be in the topmost slot, but it does need to be enabled.
