Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/e0d0a8fd3d1070b5c3b3d5e2aefa6476.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563