When you open the site via the Gmail app, go to the … menu in the upper right. You should have an option to open the site in your default browser, which should keep your session active when you get the code.

Thank you for posting this. My introduction to CAD was trying out FreeCAD when I reached the limits of Adobe Illustrator’s accuracy. The interface was so obtuse and difficult to work with I just gave up and assumed all CAD programs were like that. I’ll give Link Branch a shot!