[djbaxter]

Anyone trying to register will see error messages. If you are running 4.2.5 and PHP7 and you want to allow new registrations, apply the fix.

This is assuming you are using reCaptcha:

First check at AdminCP >> Settings >> Human Verification Options

Are you using New reCaptcha?

Then check AdminCP >> Settings >> Options >> Human Verification Options

Which boxes are checked there?

If you are using New reCaptcha, then any of the selected options will have problems and throw errors (assuming you haven't turned all errors off - if you have, you may not get an error but you still won't be able to complete those actions.