Error connecting to source, but not when PBI app opened using same credentials

Hi guys, this has got me scratching my head.

If I open desktop normally, using my user name, and try connect to a SQL source using alternate user option, it fails.

BUT, when i open the desktop using those same credentials(shift right click on .exe, 'run as ...') and then connect to the source using current user, it works.

This is not holding me up, its just a ball remembering to do it when i work on that report. also the user cant publish so I need to upload it manually.

It would be nice to understand why

any ideas?

cheers

Ian