I am having a problem installing OpenProject Community Edition on a Synology NAS, model DS920+

I first went to the Synology instalation instruction page: https://www.openproject.org/docs/installation-and-operations/installation/synology/

There it explains that:  Synology offers NAS devices that come with a UI for starting docker containers on them. This means OpenProject has to be used exactly as described in the docker section.

So I went to the docker section linked, which is: https://www.openproject.org/docs/installation-and-operations/installation/docker/#recommended-usage
I then followed, exactly as described, the instructions for installing OpenProject, and got no errors, as shown here:

The instructions then say that: After a while, OpenProject should be up and running on http://localhost:8080.

So I go to to that URL for my NAS, and get, after a few minutes wait, the following error:

Everything appears normal on the NAS, with low CPU and memory usage:

And plenty of disk space:

As you see from the browser image, I am using a URL for my NAS across my local LAN: http://192.168.1.149:8080/, which always gives the "service unavailable" error. BUT I can always succesfully reach my server's website at http://192.168.1.149 and my DSM at http://192.168.1.149:5001

Can anyone please help me with this problem?