I’m on OS 2.5.1A and the only way my NP2 see anything thing connected to it is to go into Connection Preferences > Scroll down to Improve OTG compatability and to enable this option. ( you should get a pop up notification and then select File Transfer) Mark sure the device is connected or connected within 10 seconds of enabling OTG to the phone .
ANOTHER way I get to OTG is from the Settings I just search for OTG.
I can’t remember if this option was available before I enabled Developer Options, so if not you have to enable the Developer Options.
PS: Sadly you have to do each time you want to connect via USB (Well at least I do).
😉
