I tried installing Microsoft Office Professional Plus 2010 on a laptop with Windows 7. There was a trial version preinstalled, but I put this one on anyway, since I bought it on ebay and it appeared to install okay on another computer with XP. I'm supposed to be able to install it on 3 computers.
I entered the product key on the laptop, and it appeared to install fine. But when I went to activate it, it gave the message it "cannot be activated because the product key is not valid." At this point, it didn't give me the option to even enter the key.
One forum said I should uninstall the trial software, since there could be a conflict, which I did. No luck, same message. There was a telephone registration option where I entered a 25 key code. The automated voice said it was invalid also.
Some forums said that counterfeit versions were sold on ebay. Maybe I got one, but would it have worked at all? How can I resolve this?
It may have worked for a time, and then automated checks Microsoft builds into its products would have blacklisted it. If you are sure it is a legitimate copy, then you can try speaking to someone at the Microsoft activation call center about it, but it really does sound like unfortunately you were sold pirated software.
There are no guarantees, but if you report the seller to Microsoft, it's not unheard of for them to toss free copies of software at people by way of a reward.