I am having the same issue with a 2020 demo version of Sketchup. I made sure to download the 2020 version of the Sefaira plugin, and I have re-started and re-installed the plugin several times with no luck. I keep getting stuck on the login screen. When I push “next” nothing happens. I will add that the Extension Manager says the Sefaira plugin is “unsigned”.
Could you please make sure that you have Internet Explorer 11 or later installed on your machines and then run the attached Registry file. Make sure that all instances of SketchUp is closed when you run the .reg file. The file ensures that Sefaira is looking for the latest version of IE on your machine.
Please let me know if that solves this issue for you.
Thanks Niraj, you already helped me out, thanks again!