I have a license acquired in 2017, and I had been using it with version 5.1, suddenly it stopped working and the link to download it no longer appears, I ask you to inform me if the acquired license works for the latest versions of the program. I use Mac Big Sur.
Unfortunately macOS Big Sur introduced some compatibility changes that broke WireframeSketcher. The solution is to upgrade WireframeSketcher to the latest version. There are probably other options but they are less straighforward. For example you can run an older version of WireframeSketcher in a virtual machine like Parallels with an older version of macOS. Or you can choose to use the Windows version if you also own a Windows PC.
Version 5.1.0 is not available from our website anymore but I still have it around and can upload it online if needed. Let me know and I'll send it to you.