Question:

My agents are seeing the CAPTCHA test where you have to put in a number to prove you're not a robot all the time. But when we put in the answer, it never works, even if it's definitely correct.

Answer:

Your firewall is blocking traffic to Google's reCAPTCHA servers. You should enable outbound traffic on port 80 to Google's servers - see this article for details.

If you are getting the CAPTCHA all the time and can't log in, access your helpdesk from a different IP address. In Admin > Settings under Rate Limiting, you can whitelist your internal IP addresses (so agents connecting from there don't see CAPTCHAs) or disable Rate Limiting altogether (so CAPTCHAs are never shown).