Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/92b3df05f4c3a1e549d3ce5957998195.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563