NorthernCostumeHire

We've recently changed computers from Windows to Mac and I am having issues with Express Invoice. Firstly, if I download Express Invoice via the website, it won't install once dragged into the applications folder but I can install it via the App Store. However I can't see a way to put in our registration code to upgrade the program? If I click on upgrade and then restore purchase, it says it can't be verified... Can anyone help?