Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ca7d1b14a36719be54c3b9a94a677d5d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563