What version number of minecraft are you using? 1.9? What happens if you try 1.9.2?
If switching versions doesn't work, the next thing to try is uninstalling your minecraft launcher, deleting your minecraft folder from your computer, then logging in to minecraft.net and redownloading the minecraft launcher - that will give you a fresh start, if it's a problem with your minecraft launcher
Remember to get the Desktop < for windows launcher (not 'for windows 10')
If you already have an account on minecraft.net, you shouldn't be charged again for redownloading the launcher.