Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/19d9b2b984c3c59266d9eb5b39f2a8f2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563