If you are seeing a warning that says “Windows Defender SmartScreen prevented an unrecognized app from starting”, that’s just because we recently released a new version. Windows shows that warning out of an abundance of caution when it detects a (version of a) program that isn’t in widespread use yet. If you downloaded Pencil2D from the official website, you can safely bypass the warning by simply clicking “More info”, and then “Run anyway”. If it’s another issue that you’re experiencing, you can also check out this topic for other potential solutions: