Admin Page is working, but not showing the models of my project after deploying to Vercel

I just created a project with the name “APExpress” and an app with the name “Aufträge”. When developing (python everything works fine, I could add new model data or edit data. But now, after deploying to vercel, the main admin site shows up, but when I want to add/edit data and click on a specific model, I get an 404 Error, raised by “django.contrib.admin.sites.catch_all_view”. With the request URL https:/
I assume vercel has a problem with the german umlaut ä but I don’t know exactly. Is there a way to overcome this issue?