Light room won't accept my license number on my computer at work . I want to use it at tea breaks and lunch time breaks just to get some practice in so I have more idea what I am doing at home. I just get a red X after typing the number. At home I have installed it once then uninstalled and re installed but only on one computer and it works perfectly. I only get this problem on the work computer.
One possibility is that your serial number is for a different version of Lightroom than you have installed at work.
So, what version of Lightroom do you have at work? What version of Lightroom do you have at home?