Hello,
We had a hard drive go bad and had to replace the hard drive and re install Autodesk inventor 2011. The computer is the same just new hard drive. Screen says needs activation. Hit activate enter sn and key. Connect now and activate option asks for s,n when entered says "The serial number you entered is not valid" When requesting activation code get the same message.
Thanks
Mike
Welcome to the community Mike.
Your issue is likely caused by the fact that your Inventor 2011 was either upgraded or cross-graded into a new suite, or was once under Subscription, was auto-fulfulled to a new version, and/or then expired or lapsed. Your most recently owned license may well be a newer version of Inventor. Your Reseller or philip.s here on the boards can probably assist you with this.
Good Luck!