You need to contact Adobe customer support directly as this is a user to user forum and we cannot resolve issues with your serial number.
Just a tip also you really don't want to post serial numbers where anyone can see them.
You probably downloaded the Lightroom Creative Cloud version. Your Perpetual License key will not work.
Uninstall the existing version of Lightroom, this process will not affect your Catalog, Preferences or personal files.
Then download the correct version from the link below, install and enter the license. Every thing should be just fine. (Also by displaying your License Key for all to see anyone can use it to have a free copy of the program)