Using an alias to a NAS folder on the Dock

So this worked perfectly in Big Sur, when I added an alias for a folder on my Synology NAS, then added it to the Dock, I could click on the icon and it would open the folder. Simple.

In Ventura, I got it to work but the icon, rather than being a Folder icon, it looks like a corner-turned sheet of paper, like this:

...but it still worked (even Apple Support couldn't find out why it isn't viewed as a Folder!)

Now, however, I can't get it to work at all, since I've reformatted and reinstalled macOS. I haven't touched the NAS.

I can copy the Alias to the Desktop and then drag a copy to the dock and it will work (apart from the icon), but if I delete the Alias from the desktop, it won't work. And I can't seem to drag a copy of the Alias from the NAS directly to the Dock.

I'm probably missing something, but it definitely worked before, but I can't remember how I did it, so any help would be appreciated.

Thank you