NGINX: Permission denied

I have installed and configured DataGerry together with nginx as described in the documentation. However, when accessing the website I get 502 - Bad Gateway, the logfile from nginx shows:

2025/07/17 08:00:25 [crit] 2580#2580: *1 connect() to 127.0.0.1:4000 failed (13: Permission denied) while connecting to upstream, client: xx.xxx.x.xx, server: localhost, request: “GET / HTTP/1.1”, upstream: “http://127.0.0.1:4000/”, host: “xxxxxxx.yyyy.cloud”

I started nginx as user datagerry as a test - no success.

Versions:
Rocky Linux 9
DataGerry: Version 2.2.0, Release 1.el9
nginx: Version 1.20.1, Release 22.el9_6.3

Can anyone help me?

Thanks,
Thomas

Solved, it was a SELinux Problem. I disabled SELinux for testing the software, now it works.