Cannot mount Network Storage - "stop included in transaction"

Hello everyone,

I have been trying to get this to work and I haven’t found this specific set up while looking in the forum posts, so maybe there’s someone who can help.

I tried to mount a Synology drive and created a shared folder there. I even created a “HomeAssistant” use to access the folder.
When I go into HomeAssistant and try to set everything up, it looks like this:

When I try to connect, I get the following error message: (Ignore the specific name. The screenshot was taken when I tried a different name.)
Bildschirmfoto vom 2024-12-04 19-52-50

When I close the window, I do not have any network storage connected.

Here comes the weird part: My HomeAssistant runs on a 1TB hard drive. Checking the “storage” tab in HomeAssistant tells me, I still have ~1500GB unused. That means I magically generated more storage than is available on my hard drive.

Checking my docker container (?) with docker exec -it $(docker ps -f name=supervisor -q) bash and navigating to data - mounts, it shows me the three attempts I have tried before:

docker

So somehow it did mount something, generating more storage, but does not show me in HomeAssistant and does not give me the option to select it as an automatic backup location.

I lack any competence in that area and have no clue how all of this works. Can anyone help me here?
Thanks for your time.