Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5f9778786bb7d36a0ceb5c1bda3a9be5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563