It appears the link has expired or you've used a browser that was wrong configured. Luckily for you, this process can be used over and over again until you succeed with the activation. I recommend you remove the application and delete the email you received. After this process, simply reinstall the application, but this time use a desktop browser and make sure to click the correct link and it work. Typically, it should work from the phone's browser, but sometimes error might appear.
