Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0f74cd78327e2c59705e96e0f4f11edc.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563