Captcha validation it's not working appropriately

Summary

Sometimes Captcha it's not working appropriately when you enable the Login-free portal. While trying to submit a request the users receive the following error message on UI:

We couldn't verify that you're not a robot. Try sending the request again.

But Jira it does not even provide the users the ability to verify at all.

Workaround

Contact Support channel to apply a fix.