Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3e77f8e8c1ad9286fc0efae24f0f6f7e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563