I stumbled on to a problem similar to this (if not to say the same). At first I only had set my form decorator to be my custom ViewScript where I displayed my elements, very simple and straight. But when time came to "submit", no errors showed even though I clearly set errors in the inputs.
In order for my messages to display (in order for my form to actually get the messages, because
$this->element->element_name->getMessages()
was giving me nothing) I had to add the default 'Form' decorator to my Form's decorators, ending up with two: the custom ViewScript and the Form.
I tried looking through the code of 'Form' decorator, but couldn´t pinpoint why this was happening. I was wondering if anyone knew, because I'd like to learn.
Thanks!
Here is very useful document to trace and solve your error.
i think this LINK would be very useful to you to make things working at your end. just read and try to understand carefully
let me know if i can help you more.