If no data is being sent from RTP to Google Analytics, make sure that the segment in question is linked to GA
Go to the Segments page
Edit the segment in question
Make sure Send segment to web analytics is checked on
Without this field checked, no data will be sent from RTP to GA regarding that segment.
To validate that RTP is sending data to your GA account, first log in to your GA account, and make sure the segment data is being populated in GA.
Navigate to Reporting > Behavior > Events > Top Events > Segments (Event Category) > Event Actions
If you find that some, but not all, of the data is being transferred from RTP to GA, visit this article to learn why there might be discrepancies.