connector e-mail

Hello, I created a service and it assigns an email Send connector. I configured the parameters and time to test sending in own connector configuration screen it displays the following error: Unsupported expression type for testing: -input Parameter 'message' use the expression containing unreachable reference

What will I be doing wrong:

Bonita version 6.4.1

Hello,

I am using version Bonita BPMN Community 6.2.2. and I am new in this. Trying to make simple process: Employee asking for permission, Managers approves/denies and employee should get e-mail notification about result. Most of the time this part (sending email, done by System) fails, no email and status is: Failed. In best case status is executing, but e-mail never arrives. Currently: SMTP Host: smtp.gmail.com Port: 465 Username: mygooglmail@gmail.com Pass: My password (checked, correct)