Manual update to 2.6.2931 After uploading the app-new folder to my server, renaming it and logging in to the admin area. The website responds with a 'System not available message' (in Dutch) for both front and admin end.



Resetting the app-old as the default app folder again does not solve the error message. I've cleared the storage/runtime/cache and storage/runtime/compiled_templates folder. 

What actions are needed to restore the site to working order first, before going into the update again?
Replace the /app folder, per the Manual Update instructions. It sounds like you may have already done this, but rolled it back.

Once the new /app folder is in place, you must visit the admin section. This will run any necessary migrations.

That's it!