Why am I not seeing the captcha challenge?

Make sure you are not blocking Google services 

If the reCAPTCHA does not show up and the only thing you see is a "WARNING" box (see below), it is likely that your local setup, browser, firewall etc. is blocking Google services. In this case, we recommend trying a different browser, disabling browser plugins that might be interfering, or unblocking Google services manually.

Why am I being presented with a reCAPTCHA challenge?

To protect our website against spam and other automated or malicious activity, we rely on reCAPTCHA - a free service offered by Google that blocks bots, while letting humans through with ease by merely ticking a box.

Note that the vast majority of users will not be presented with the reCAPTCHA challenge in the first place. Only if you happen to raise a flag by e.g. trying to log in repeatedly within a very short time frame, will the reCAPTCHA appear.

This is what the captcha challenge will look like:

To proceed, simply tick the box that says "I'm not a robot" and you'll be able to move on as normal.