"Could not send message" when using tibco spotfire nodes

When trying to use any of the TIBCO Spotfire nodes (file reader, writer or information link reader), I always get the “Could not send message” file:

ERROR TIBCO Spotfire File Writer 3:246 Exception while loading types
WARN TIBCO Spotfire File Writer 3:246 Error uploading to library: Could not send Message. … Retry number: 0

Could this be caused by providing the wrong URL? I am not sure how it should be structured; if I am writing to the library, should the path to the output files or information link start with “Library” after the server url? Any example would be useful, as I cannot find any in the documentation.