Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5a6a271d2e2d4b2dd949061e41d554ab.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563