I tried to send a sample registration using the Payment by Check option & received an Authentication/Authorization Failed message. Why?

Please note that when the payment field is displayed on the form, the payment must be made using the online payment. If you want to enable the payment offline by sending a check, you may consider setting up a condition to hide the payment field on the form. Please refer to the guide below that can help you with this.

https://www.jotform.com/help/120-How-to-Set-up-PayPal-Along-with-Other-Payment-Options

Thanks!