Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3ce4b446f8d5af5e9b3f750c6e5f5dc4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563