Look at the bottom of the error message: “The most likely reason for this error is that the selected font has not been installed for all users. See FAQ.” (Although I don’t actually see this issue in the FAQ…)
When you install a font it can either be installed for the local user or for all users. (Right–click on a .ttf font file and you will see those two options.) Only the latter option puts the font into the system fonts folder. (The other puts it in appdata somewhere.) PTXprint requires that latter option. I don’t actually know how you can tell where it is installed from the Fonts Control Panel. You can try in Windows Explorer browsing to an address of C:\Windows\Fonts, and I would assume that fonts installed for the local user won’t show up there. Anyway, an easy way to make sure is to uninstall your AS font from the Fonts Control Panel, and then install it explicitly for all users (right-click on the .ttf file and select Install of All Users).
Hope that helps,
Jeff