Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5196c74b62c44b1f73d68b7e09d5bcbb.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563