Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/e3ef521c4e4d4d6ca05d0e0f0b699803.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563