The problem is that app security restricts access to the SD card unless it is a built in app. If Photos is pre installed then it is fine. If it is installed from the play store it lacks the proper security permissions of built in apps.
Posted via the Materialistic Android Central App
I know this is an old post, but for anyone finding this through Google like I did, I figured out a fix for this. I was selecting photos and then hitting the trash can button when I got this error message. Instead if using the trash can, click the three dots in the corner (the overflow menu) and click "delete device copy." You will then be prompted to give Google Photos access to your SD card. Click "allow" and problem solved.