Catchable fatal error: Argument 1 passed to Phalcon\Mvc\Model::validate() must implement interface Phalcon\ValidationInterface, instance of Phalcon\Mvc\Model\Validator\Email given in C:\xampp\htdocs\invo\app\models\Users.php on line 13

Phalcon\Mvc\Model\Validation is now deprecated in favor of Phalcon\Validation. The functionality of both components is merged into one, allowing us to reduce the codebase while offering the same functionality as before.
Previously validations were implemented as follows:

namespace Invo\Models;

use Phalcon\Mvc\Model;
use Phalcon\Mvc\Model\Validator\Email as EmailValidator;
use Phalcon\Mvc\Model\Validator\Uniqueness as UniquenessValidator;

class Users extends Model
{
    public function validation()
    {
	$this->validate(
	    new EmailValidator(
	        [
	            'field' => 'email',
	        ]
	    )
	);

	$this->validate(
	    new UniquenessValidator(
	        [
	            'field'   => 'username',
	            'message' => 'Sorry, That username is already taken',
	        ]
	    )
	);

	if ($this->validationHasFailed() == true) {
	    return false;
	}
    }
}


Introducing Phalcon\Validation, you will need to change the above to:

namespace Invo\Models;

use Phalcon\Mvc\Model;
use Phalcon\Validation;
use Phalcon\Validation\Validator\Email as EmailValidator;
use Phalcon\Validation\Validator\Uniqueness as UniquenessValidator;

class Users extends Model
{
    public function validation()
    {
	$validator = new Validation();

	$validator->add(
	    'email', //your field name
	    new EmailValidator([
	        'model' => $this,
	        "message" => 'Please enter a correct email address'
	    ])
	);

	$validator->add(
	    'username',
	    new UniquenessValidator([
	        'model' => $this,
	        'message' => 'Sorry, That username is already taken',
	    ])
	);

	return $this->validate($validator);
    }
}