Kodi cannot see HDD connected to Nvidia Shield Pro



Hi everyone,
I am having issues with finding my files from an HDD on Kodi.

I installed Kodi 21 on an Nvidia Shield Pro. I’m trying to get Kodi to scrape all the files from an external hard drive I have connected to my shield, only there isn’t an option to actually add the drive as a source. 
I have already set all permissions correctly for the Kodi app on the Shield.

When going into the Kodi settings/Media/Library/Videos I can see my HDD and all my movies, but when I go into Files/Add Videos/Add video source I cannot find my HDD, it only shows External storage (which is actually an internal storage, as it shows the files in the Kodi internal drive) Network File System, Root filesystem, video playlists, windows network (smb), zeroconf browser, add network location. 

I have no access to my movies via the main menu.

Does anyone have an idea? I am stuck and cannot find a solution.

​​​​​​​Many thanks in advance