I don't know how this forum thing works, but customer support said they could not help me with my problem and that I needed to find the answer on their forums. I have purchased lightroom back in 2013 and I tried to get in it today and it will not open. When I go to update it, it says that my trial has expired. I can not reregister my serial number and customer support says it is to old of a version and they cannot help me. Can anyone else help me. I've never used forums and I am computer illiterate.
I'm guessing that you probably have Lightroom 5, or it could be Lightroom 4. In either case, when Lightroom is first installed, it can be installed as a trial version that expires. If that is what happened in your case, on the screen that indicates that the trial has expired there should be an option to enter your serial number or to make a purchase or something similar. If you choose that option then you should be provided with an input screen where you can enter the serial number.