Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f2a1d8a260dce7ccf4a0785e634f59d4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563