If the converter isn't working for you, please read the following tips. If you don't understand how to use the converter, please first read the main converter page.
If you don't see anything, or you see an error message, you may not have a working Flash Player. Try downloading it from here. If you see an alert about a security risk or outdated Flash player, just allow it to run. It is not dangerous and will not make any modifications to your computer.
Are you using an incognito window in Google Chrome? If so, there is a bug in Chrome's built-in Flash Player which stops Flash from saving files. Switch to a standard (non-incognito) window or a different browser.
Make sure to save your file with a SWF extension so that your computer can tell what type of file it is. For example, name the project Game.swf when you save it. If the converted file is already on your computer, you can simply rename it so that it ends in .swf. If your computer is unable to find a program to open the SWF with, try using a browser. You can also download a standalone Flash Player; however, it is not usually necessary. Your computer already has a Flash plugin if you can use the converter.
First, ensure that you are converting a valid Scratch project. Try opening it with Scratch to see if it is corrupted. If it is an SB (Scratch 1.4) file, try opening it in Scratch 2 and then saving it again in the new SB2 format. Then, try converting the project with the default settings. Don't check any boxes or change the width and height. There is also a known bug in the converter caused by a new security restriction in Flash Player 23+ which can prevent SWF files saved locally from loading. See the known problems page for more information.
If these tips don't help you or you're having a problem not mentioned here, there's a chance that you've found a bug that I don't know about. Please see the known problems page. If that doesn't help, why not contact me? I may be able to help you, and that way I will know about the problem.