rpandita, thanks for quick answer, but accounts.adobe.com/products page only lists the serial number that is reported as Upgrade serial number when I try to enter it on the licence tab of Lightroom application, I cannot find original serial number anywhere, probably it was printed on DVD box that I can't it find anywhere. Is there a way to restore the original serial number?
I didn't re-install Lightroom since the original installation so probably original serial number is stored somewhere on my laptop.
I have sent you a personal message, please check it and reply
@rpandita, thanks, but the serial number you've sent me in personal message is the same one I already have. Also your suggestion to contact customer service doesn't work for me - I've already contacted them but they've said Lightroom 4 is no longer supported and I need to post my questions on the forum.
Looks like since I've updated from Lightroom 3 to Lightroom 4, now even I want to use version 4 only, I have to have Lightroom 3 serial number which I've lost.
That's a very frustrating experience - the software that you've purchased a long ago that was working, stops working at some moment and there is no way to fix it.
I was considering to upgrade to version 6 but apparently I need to change my plans and look for other alternatives.