Session Expired Immediately

I have a Vaadin 8.6.1 application. When running local, there are no problems. When in production, I get the “Session Expired” banner immediately after the page is loaded.

We are running Tomcat 8.5.55. I verified that the JSESSIONID is being set.

The following is logged under the debug window:

Received xhr message: for(;;);[{"changes":{},"resources":{},"locales":{},"meta":{"appError":{"caption":"Session Expired","url":null,"message":"Take note of any unsaved data, and <u>click here</u> or press ESC key to continue.","details":null}},"syncId":-1}]


Response didn't contain a server id. Please verify that the server is up-to-date and that the response data has not been modified in transmission.

The end of the log sometimes has:

No active request.

I noticed that when the error does not occur, the “syncId” property is not -1 and the xhr message contains valid data. I have tried disabling push, but oddly enough when it is enabled with WebSocket transport, it fails and reverts to Long Polling.

Any ideas? Thank you all for your time.