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?