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!
Did you backup the database before trying to install the new version?
The new update might have messed something up with the DB so the previous version isn't working with the old version of /app. So you might want to try re-add the old DB and previous version of /app.
Thank you all for your thoughts, pushed me into th right direction.
There was a mismatch between the db version and the app/ folder version. I took the latest SQL backup and downloaded the corresponding Craft CDN repository installation. Imported the SQL backup into the database, and uploaded the corresponding app/ folder.
After checking all functionallity updated to the latest build. All is working as expected again !
-R
