I had problems registering my LR6 and I managed to fix it today. Not sure if you are experiencing the same problem and error message but I will describe what my problem was and how I fixed it ... Perhaps, it may help.
Last year I bought LR stand-alone to upgrade from version 3 to 6 and I installed it on 2 PCs - no problem.
Now I needed to install LR6 on a different PC so I first uninstalled LR6 from the second computer and then downloaded the software from my Adobe account (Note: the download includes the LR6 serial number) . The software was installed on my new computer OK but I got the following error when trying to activate the software "Serial Number you provided is valid but a qualifying product could not be found on this computer".
I tried many times both signing in and manually entering the Serial Number for LR6 but to no avail - same error message.
Then it occurred to me to try to enter the Serial number for LR3 ... and problem solved. (I found the Serial number for LR3 in my Adobe account history)
Hope it helps
This is not entirely correct.
- A download never has a serial number integrated.
- Removing/De-installing a software from a PC does not guarantee to de-register it with Adobe and it will not free up one of the 2 activations you are allowed to make with a single license.
- There's no need to remove if you need to have it activated on another PC. You can simply sign out using the Help menu of LR and/or the Adobe Desktop App. You can have it installed on more than 2 PC's/Laptops/Macs but only 2 can be activated/signed in.
- If your serial is an 'upgrade' serial, you always need to enter the serial of an older version too.