I want to install Lr 5 on my new laptop. I enter the correct licence number and keep getting the message "The serial number you entered is invalid. Please try again" I purchased Lr last year and have it installed on one other computer, which I want to uninstall from once it is up and running on the new machine (I understand you can have Lr installed on 2 machines under 1 license??)
You probably installed the Adobe Creative Cloud version in error. Your perpetual license will not work. Uninstall you existing copy of Lightroom this will not interfere with your Catalog, preferences or personal files, download the one from the link below and install and you key should work just fine.