It is always worth looking on the flows site when trying to find useful nodes. That site has lots of information about each node which will give you some clues as to how good it might be (or otherwise). As with all open source platforms, not all of the contributed nodes are of the same quality or get the same level of support.
In this case, you can see that the node hasn't been updated in over 4 years which isn't necessarily a good sign if you are having issues getting it to work.
I do have a Synology NAS but I've not used this node and it doesn't say which versions of the Synology API's it might work with.
So there are a couple of things you can try.
Firstly, you could try raising an issue against the node on GitHub and see if the author responds.
Secondly, you could try to explain in the forum what you'd like to achieve. Maybe another forum member will know how to do it and might help.