Lightroom 5 is asking for the key of my before lightroom version to activate my new key ... but i never owned lightroom before and so i have no older key so what can i do now to activate my licence? lightroom shows me that "this is a update key. the serial number of your previous lightroom is also required."
You bought an "upgrade" of a previous version of Lightroom, instead of the Full Version which doesn't require a previous version's serial number. You'll have to talk to Adobe to straighten this out.
Okay thank you.