I've tested several times and I keep getting a "Security Error" message

I've tested several times and I keep getting a "Security Error" message. The form is also defaulting to a PayPal Pro and not allowing me to do a regular PayPal account. Please advise.

This issue usually happens when the credentials used are incorrect or used on the incorrect environment, please kindly make sure the credentials are for live environment and your integration is on live environment too. You can check this by editing your form on the builder, searching the integration and clicking on the wand icon to get into the settings. 

Also, note that the payment integrations are different and if you need to replace the current one with PayPal Standard you will need to delete the current payment field and add the new one. 

If you continue experiencing the issue, let us know.