I am getting a “Recording error!No access for recording” message when trying to start a recording on my 2017 Nvidia Shield TV. I configured ProgTV to use a flash drive that is formatted as NTFS and is recognized by ES File Explorer. My version of ProgTV is 2.37.6.0. The flash drive is NOT being used as internal storage.

Check app permission in Android settings.

Storage permission is on.

Hi, I am having exactly the same problem.
Have tried everything

Try select other folder. For example download folder not request addition rights.

I want to record to an external source so that I can increase the storage space and also to remove it and play on a laptop

Modern version of Android not allow record to external devices. Need changes of Android config. Or can you give me hint about fix that on app side?

This is due to new Android 6+ write restrictions. If you didn't have realized, there's a folder called Android/data on any external storage to write new data because this app don't ask for write permission to user.
As of Marshmallow, it's impossible to write to the root directory or any other folder of any drive without asking for permission first. It seems your app is not asking for permission, so you must use a specific directory. Follow these steps:
1. Find out the name of the package corresponding to the ProgTV app i think it's com.progdvb.progtva
2. Create a folder called 'Android/data/com.progdvb.progtva on root directory of your USB drive For example, Kodi data directory is /Android/data/com.org.xbmc.kodi/
3. When you are going to record a new show, select this new folder for recording. If I'm not wrong, the app will have write permission and you're done.

PS: ProgTV Beta package name is com.progdvb.progtva_adv

What permission I can ask from app side?

ProStock,

Thanks! Recording to usb works perfectly now adding that folder location.