user credentials rejected by pgAdmin right after new install

Hi,

I have to install postgres on my QNAP TVS-1271U-RP but am no pro, so
hopefully this is an easy beginners mistake:

- via DockerStation on the QNAP I installed postgres and pgadmin via this
docker compose <https://github.com/khezen/compose-postgres>
- the only thing I changed in the process was the POSTGRES_PASSWORD in
the yml.
- after successful install I went to pgadmin, clicked "add new server"
and entered the server's ip address along with the POSTGRES_USER and
POSTGRES_PASSWORD values from the yml file.
- However, pgadmin says that those are the wrong user credentials.
- I logged into the docker terminal for my docker container and checked
the environment which confirms the above values are indeed correct.

I used to have this running once in the past but decided to uninstall
everything and start from scratch for several reasons. After several hours
of trying I just cannot figure out what I am missing to get this going.

If someone would be able to assist with this, that would be amazing.

Cheers,
frank