Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/986e9ba49f6ae46f11b68f7cb1d3aebe.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563