Back in 2008, Bluetooth File Transfer (Windows) was released compiled with .NET Framework 2.0, in order to (hopefully) make it as future-proof as possible. Unfortunately, this short-sighted choice has led to compatibility issues. Newer releases of the .NET Framework broke retro compatibility with older versions, and in the latest Windows operating systems, .NET Framework 3.5 (and lower) is only available as an optional package, as explained in the FAQ section.
To make matters worse, even after installing .NET Framework 3.5 on Windows 10/11, the operating system somehow blocks the automatic license key request (via HTTPS) to our server, preventing you from receiving a free license key seamlessly.
As a temporary solution, you can manually generate a FREE license key in the application page. We are currently working to locate the original source code (currently lost 😢) and release a new version of the app that addresses these compatibility issues.