Are your Web Users getting this error message when trying to login in after the upgrade to 6.5? It happens if the local web browser cache is not updated. If you look underneath the login window you see that it still says v 6.4, while it should say 6.5.
1) Enable/use a “Private/Incognito” window on the used web browser then try logging in again. To get to the Private/Incognito if you are on a windows machine at the same time hold down the Ctrl key on your keyboard, Shift and N. On Mac hold down the Command key, Shift and N. Then, in the web browser use “shift” key + “Refresh” button on the web browser until “v 6.5" appears below the login screen as opposed to “v 6.4"
If login still does not work from here
2) Clear the cached data within the browser.