Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f3a7447dc362f8e0c57766f2301b4218.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563