Sametime client logins no longer work after Sametime server software upgrade. The embedded notes basic client shows Logon successful, but nothing the status still displays as Disconnected.
Standard clients may give an actual error message: "Application version does not match the server version. User should upgrade".
In addition, if logins are being logged, this message will be visible under under the Logging --> Community Logins/Logouts view beside each client's embedded Sametime client (in this case) that is an older version.
Upgrade the Notes Client to the latest release. (In our case, Lotus Notes Basic 8.0.1 to Lotus Notes Basic client 8.5.2.)
Change the security setting, VP_SECURITY_LEVEL=xxx to a lower number than currently installed, or even 0 for any ST server or client.
(In our case, we changed, VP_SECURITY_LEVEL=7000 to VP_SECURITY_LEVEL=0.)