500: internal server error when opening .ipynb

I am using jupyter notebook via anacondaprompt now for 3 years. The problem is now when opening a code (or make a new script) I get a blank tab with: 500: internal server error. I have tried to delete cookies and cache. Further I updated via anaconda jupyter notebook using the commands: conda update jupyter notebook an conda update --all. This did not work either. How can open my codes and get rid of this error?

I also turned my computer on and off. tried to find it using google and even tried chatgpt without any luck.