Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2b8a6f5d6d18cb500d94e0d6a602b657.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563