I reinstalled Windows but forgot to deactivate my product (CS4 Master Collection) before doing so. (This was the second computer my product was installed on.) After reinstalling Windows, the license key no longer works, even on the same computer. Adobe aparently sees it as still being installed on the old Windows system, and I have no way to get on now.
Adobe Support would not assist me because I am a second user and was unable to transfer the product registration to my name. Strangly enough, I did successfully "register" the product, and Adobe's website says the product is affiliated with my Adobe ID, but tech support said differently.
Once deinstallation is finished, the only way to fix it is to reinstall the software and then purposefully deactivate it - but if a system is completely wiped then that won't work...
Unfortunately licensing issues are something that only Adobe Customer Service can assist with... This is a user-to-user forum and we here do not have the means to "reset" your installation count. So hopefully in cases like these you can sort it out with them directly.