The message, “This is not a Test User account”, is only shown if you’re using a non-sandboxed copy of Composer for Mac, and it cannot find a valid App Store receipt for a purchased copy. Since the non-sandboxed copy is not itself authorized through the Mac App Store, you can’t simply user your iTunes authorization credentials in that dialog. You may also see the message, “Please create a new account in the Sandbox environment.”
Note: Remember, in order to use the non-sandboxed copy, you must have a copy of the regular App Store version installed.
If you have the App Store version installed and it still won’t run, you can copy the receipt manually. You will need to copy the file:
/Users/<your user name>/Library/Application Support/MultiMarkdown Composer/receipt
MultiMarkdown Composer folder doesn’t exist, you can create it.
NOTE: If your machine is not running in English, you will have to modify the above paths to suit your system.
If you’re doing this in the Finder, you will need to right click on MultiMarkdown Composer and “Show Package Contents” to see the inside of the application bundle. Similarly, your user Library may be hidden in the Finder, in which case you can use the menu item “Go:Go To Folder…” to gain access.
Once a working receipt has been installed, you do not need the App Store version installed any longer.[an error occurred while processing this directive]