Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8ac2897e350d545c0ace6eb4ac5d7609.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563