Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2b965b85a5d2f0658e2beb2de1e9f1a1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563