Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c6bb6c66f547b3db779f0893f93e9376.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563