942-undefined-invalid credentials before Hosted Tokenization iframe is submitted

Hi there,

I'm implementing the Hosted Tokenization iframe into my react.js site. I'm developing on localhost, so I created a profile without a source domain in order to bypass source URL authentication. When the page containing the iframe loads, the following error is displayed before the iframe form has even been submitted. 

https://esqa.moneris.com SENT - 942-undefined-invalid credentials
 
What could be causing this error to show before the form is even submitted?
 
Thanks!