Ok. Your reinstallation of eu4 has nothing to do with what you're describing.What details do you want? When I click convert it stays at 0% and then after 57 seconds it just says error
It sounds like the frontend couldn't start the converter because it was blocked either by an already running one or antivirus or something else. Restart your computer, delete the converter and unpack it again from the zip, then retry. If that fails try disabling antivirus.