Unable to deploy and display saved forms

I installed Kobotoolbox on my own server.

My commands:
apt install docker
apt install docker-compose
git clone …
python3 run.py

(I accepted all default values. My own public domain is mydomain and 3 subdomains, kf.mydomain, kc.mydomain. ee.mydomain were double checked to be sure that they pointed at the same IP)

The process was very fast and I didn’t have any error.
I logged in kf.mydomain and created and saved forms but I had these problem:

  • Unable to deploy.
  • Unable to display the saved forms.
    (Access denied error with Additional detail: 504 Bad gateway).

My server is an VPS on Vultr.com with:
OS: Ubuntu 23.04 x64
SSD: 100GB

So how I can resolve my problem? Could be my server performance is not enough or I missed the appropriate permission grants?

Thanks for your help!