When I try to open sketchup pro I get a message that my subscription has expired and needs to be renewed.
What version of SketchUp are you using? Your profile says 2017 but there never was a subscription for that version.
If you have a subscription you won’t have a license and serial number. Subscriptions use the email address and password you used when you purchased the subscription. If it has expired you’ll need to renew it at sketchup.com to continue using SketchUp.