Check the box next to "Show verbose output during: > compilation
Click "OK"
Sketch > Verify/Compile
After the compilation fails you'll see a button on the right side of the orange bar "Copy error messages". Click that button.
In a forum reply here, click on the reply field.
Click the </> button on the forum toolbar. This will add the forum's code tags markup to your reply.
Press "Ctrl + V". This will paste the compilation output between the code tags.
Move the cursor outside of the code tags before you add any additional text to your reply.
If the length of the output exceeds the forum's 9000 character limit, save it in a .txt file and post it here as an attachment. If you click the "Reply" button you'll see the "Attachments and other options" link.
Weird, usually the app store version is the one that doesn't work.
The error implies that the board package (specifically it's platform.txt) is corrupt somehow, or that something is interfering with access to it in a way that doesn't produce an access denied message. I can't think of any way that either of those things could happen, though. (the above instructions would have shed at least some light on the matter, though).