I got an error code: 36006-5 and I wasn't able to start up any game anymore.
On a forum I saw that deleting the user and creating a new one might do the trick. Before I deleted the user, I uploaded my saved data through PlayStation Plus. After deleting the user I created a new user, logged in on my PlayStation Plus account and navigated to the option to download the saved data from the cloud. However, it asked me to subscribe to PlayStation Plus again.
Does this mean PlayStation Plus is linked to only one user and cannot be accessed if you create a new one. As far as I know, I used the same PS account (which is something different than just a user) back then for the deleted user as for the one I just created. Is there a way to get my uploaded saved data back?