403 Forbidden - after fresh setup

What is the problem?

Can't reach the web-frontend. Got the message "403 Forbidden" after browsing on 192.168.178.139.

What did you already try to solve it?

Ping works
SSH works
New image installed
reboot

Have you tried running in safe mode?

no, dont know how. I'm bad on using unix.

Did running in safe mode solve the problem?

Systeminfo Bundle

Raspi 3B+ fresh image with octo
Sidewinder

Additional information about your setup

Windows 11 Chrome and Android

Can I download the API-Key by using SSH? And if yes, how do I it?

Sincerely,
Jan