Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2f1abb3116697924e5b6f8e2e4601c3b.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563