Running SourceTreeSetup-3.3.8.exe on Window7

(seems like version 3.3.8 but belowin this form I selected the highest possible)

First step, "Registration", press the "Bitbucket" button.

Default web browser (Firefox) opens on: http://localhost:34106/?state=authenticated&code=TuCBZajAtRrHeS4m5Z with page "Authentication Successful", "you can close this page"

But the installer won't enable the "Next" button, so installtion is stuck