Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/1a8c2a9f190a41996d2b41b3f96f9615.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563