Hi! I'm having the same problem. I purchased my license over 10 years ago and cannot find the registration number now. Any pointers on how to find that would be super helpful - my entire graduate school and business is on my voodoo pad and it would be a tragedy to lose it.
I've tried retrieving the license through the provided link and my email address isn't recognized. I have tried every email address I've ever used and none of them are recognized. I purchased this app through the itunes store and I have proof of purchase. They do not list a license or registration number on their side of things. How can we resolve this if I can prove I purchased it?