Sum 0

Hi, for several years I am using your plugin and everything worked fine. Since last week, all the users, who make the test, get a 0 result though.
The sum function seems not to work anymore.
Now – I have tested it on different devices and it works all the time. Do you have ANY idea, why it would not work for the “real” user?

The page I need help with: [log in to see the link]