SpreadsheetWEB applications have a default time-out of 5 minutes. If there is no activity in the browser window for 5 minutes, SpreadsheetWEB will close the session and remove its data from the server. This means any unsaved data will be lost.
It is possible to change the default time-out value through server configuration options. But this option is only available in private cloud and server licences. Please contact your account representative or email email@example.com for more information.