To upgrade Pro licenses for SketchUp:
Go to the SketchUp Licensing Troubleshooter webform, and:
(1) choose “Yes, I have purchased a license.” to the first question,…
(2) choose “I would like to upgrade my license.” to the second question.
Follow the instructions.
To download new installers for SketchUp:
(1) Determine the latest version that your hardware can support:
(2a) Go get that version, and choose your language in either the Pro (last 3 version) or Make (current version only) edition:
(2b) If you need an old version of SketchUp Make for an old platform or OS: