The I'm not a robot reCAPTCHA is something you may encounter during the account login/registration process. This ensures that you are not a bot who is making accounts.
The I'm not a robot reCAPTCHA constantly spins after selecting the I'm not a robot reCAPTCHA box.
This issue can be caused by network or browser related issues.
Try either reloading the page or accessing the same page with a different browser such as Google Chrome or Mozilla Firefox.