The Lotus Instant Messaging / Sametime installation is on a "new" Domino installation. Logins were "simple" before installation.
After installation, the prompt is turned into the SameTime login prompt. Any valid username and password is not accepted. The login screen is simply redisplayed to the user. This server is the "first server" rather than a second one.
The installation switched the server to session authentication, multiserver.
Switch the session authentication on the Sametime server to single server rather than multiple server.
Complete the missing LPTA token information.
1. The Quick Way:
You can copy the Internet Site's related documents from other "main" Notes Domain if you want to take a short-cut and you have this already configured in you "main" Domain.
2. Follow the Instructions on Creating a Web SSO configuration document. Follow the instructions exactly. It is easy to miss or mess-up a step.
Search the Administrator Help: Creating a Web SSO configuration document