When I export my config as a tar.gz then import it to it’s destination it expands in a subdirectory which is not visible to the destination site (there is also no feedback that an error has occurred, see image below). This appears to be a bug.
As you can see, thought the DSM says the configuration is ready to sync there is no config to sync! It is there, it's just one level dow in the directory structure.
The workaround is to extract the tar and then re-compress it from within the directory as a list of files (tar -cvzf config-myconfigpath.tar.gz .) then import it.
Add a step to the process of extracting the tar that removes the files from the archive directory.