Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b767e7d4abf3206f8163b21d2ee948db.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563