You will, in fact, need to take this up with Trimble’s SketchUp Pro Support. Typically an authorization code is provided by email that enables installation of the newer version when you are receiving the maintenance upgrade. There may have been a time limit on the validity of the upgrade link though. It is better to install the upgrade shortly after getting it because it may have avoided your present concern and the process to move the license from one computer to another is simple and quick. You may be aware already that you can have more than one version of SU installed on your computer so both SU 2014 and SU 2015 can compatibly coexist on your hard drive.
BTW, I would expect the next version following SU 2015 (ostensibly v2016) to be coming out soon based on past history.
Unfortunately, no option for immediate phone contact with customer support exists.
Try this url: http://help.sketchup.com/en/contact/customer-support
Also see the following link: http://help.sketchup.com/en/article/3000020