Pretty self explanatory error message. I assume that you are attempting to configure the FXS ports at this time. Are you using the password that 3CX is showing, after creating the extensions? Sometimes cutting and pasting will add a space, making the password invalid. Are you setting the device to use the Auth ID?
So while 3CX doesn't stop you from using any SIP compliant device, if you don't know how to make them work you are better off using the supported devices with have templates and guides: