Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/652a6ad42d0727d87efe1e382a1c3f81.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563