To check how the reCaptcha works, please, follow the steps:
1. Open the page where reCapthca should be;
2. Open browser console (Shift+Ctrl+I);
3. Open Console settings:
4. Uncheck 'Select Automatically' and choose any kind of browser or device;
5. Fill in and submit the form.
However, Google uses its own criteria to define whether a real man or a spam-bot is trying to send you a message. One of this criteria is the user agent. ReCapthca shows the verification pictures only if it suspects a bot.