Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a94577d5baf83c9be96d0a22589f0b9c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563