I can’t Update Apple ID Settings as it prompts me with my old e-mailadress

So a few months back I changed my Apple ID adress as I no longer use my old e-mailadress. I signed out on all my iDevices and logged back in with my new e-mailadress.

Now since iOS12, I am suddenly prompted in Settings to Update Apple ID Settings. When I click this, the Apple ID is already filled in and uneditable. My current password doesn’t work and signing out and back in does not work.

I have no problems with services though (like iCloud or updating apps) but it keeps prompting me to Update Apple ID Settings.

Any help would be appreciated.