Auth Keys repeatedly failing - 4834

Auth Keys repeatedly failing - 4834

Hi there,
I am currently helping develop a Wordpress website that requires the use of a Ninja Form and ZohoCRm but the Authentication Key constantly fails, coming up with the error message "Module - Leads: 4384 - Invalid Ticket Id", even after we've changed it a few times by generating newer ones by both the Browser and API methods. 
Has anyone else had the same problem, or could suggest a solution?

Thanks all!