There is a bug in PBI Desktop Relationship when using Data Flow. Look at this image please. There is no table at end of relationship.
Hi @demetrioi ,
I tested to conenct to DataFlow from Power BI desktop (Version: 2.70.5494.761 64-bit (June 2019)), relationships were established as expected between tables.
Please clear the cache and update your desktop to the latest version for a try.