There are many problems such as an automatically unsuccessful update, etc. that can make an application stop working. Therefore, a simple and quick way to try making this application start again is to reinstall it. First of all you need to uninstall the client properly (Control Panel > Uninstall a program), then go to its official page and download the program again (you will be sure you download the best version). After the download is complete, open the setup file and start the installation process.