Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/90e7ce4cb2a42f13cef21f8e1e539145.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563