Ciao,
The website has changed last monday, and a few links are still broken. I’ll show you where to find :
once you’re connected on sketchup.com , click on the little squares then “view account”.
then, on the left page click on “my products”.
then “view included applications”
and under sketchup pro, “manage devices”
then :
After that, you might still need to logout of sketchup, then login again. but it should have released all your activations 