i will admit that I upgraded all 4 of my Macs and my Macbook Pro 15" laptop attempting to download the and update via WiFi screwed up and i had to do a recovery operation on it. Definitely do this before reinstalling the entire OS. So as mentioned above, if you cannot get it to release the pro functionality, probably need to uninstall and reinstall the app - take like 2 minutes to do this. I double-checked this with a backup folder of software installation files i have on an external HD and its the same version according to the title of the file. That's the only way to verify that you are in Pro mode other than knowing what features should be unlocked. The Pro symbol should appear after you click out of the text field to enter the key. After upgrading to High Sierra I installed QT Pro 7 via this link Installing QuickTime Player 7 on your Mac - Apple Support and then entering in my registration key.