Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3d87ce9a01fa643c6bb929d2fac1f99a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563