[Error Message] "An error occured with the human verification" on registration

[NickGHQ]

I recently upgraded to 1.8.19 and have been receiving this error when trying to register. Not sure what's causing it, what I've tried:

• forced default theme and updated all templates
  
• set new captcha keys
  
• tried again with all plugins disabled
  

**edit:**
Also receiving this when trying to reset PW or do anything that requires a captcha to be solved