-20: Error - Invalid license number

[James Jordan 0]

I am having an issue where my Nitro Pro was already registered and for some reason it reverted to a demo version.  I attempted to re-register using my serial number but am receiving -20: Error - Invalid license number. The serial number entered does not exist.
The version that is displayed in the about Nitro Pro screen is 12.16.3.574.

Please help!
Thank You,
James J.

[AllainU 0]

Hello @James Jordan,

Thank you for reaching out to us through our Community Forums!

Did the affected machine installed a major Windows Update prior to this issue?

If yes, kindly note upon the upgrade of the operating system or installing a major Microsoft update, the Computer ID is changed, as it is comprised partially by the operating system. Once changed, this will no longer recognize the original installation causing the program to revert to trial mode.

To fix this issue, I just made an adjustment on your license, so you can now activate your copy of Nitro Pro by going to Help tab > About Nitro Pro > Activate, entering your serial number and clicking Activate.

Thank you for choosing Nitro and I hope this helps.