When you run the Eikon API with a new Eikon ID which has not been used before, the "welcome screen" appears but it won't fit in the window. Therefore, it's not possible to continue. It looks like this:
The workaround is to login with the new Eikon ID in the web version at http://eikon.thomsonreuters.com/login
If you click through the first pages, your Eikon account will now be ready to use with the Eikon API Proxy.