Manually added cores won't load?

Really enjoying retroarch!

Had to reinstall and would like to use the Mame 2014 core that I have been using (mame2014_libretro_android.so) and also Mame 2010 (mame2010_libretro_android.so)

I manually copied both to the cores folder on my nvidia shield tv but can’t get retroarch to load either.

I tried a few other cores and it seems that any core I manually copy to the cores folder will show up in the list but not load. Anything I download via the core updater loads fine.

It wouldn’t be an issue but neither core I want is available through the updater.

Anything I can do here? Thank you

edit – I guess I need to change the file permissions

edit 2 – made sure the files had read/write permissions (they already did) and set file ownership to the retroarch application, but anything I manually add to the cores dir still will not load?

Any idea what I need to do? Any chance last working Mame 2010 and Mame 2014 cores can be added to the updater? Thanks for the help