With samsung IP phones (including softphone) the extension numbers and user id's don't have to match.
This is not the case with SIP extensions.

The OS softphone as a standalone software was discontinued.
They decided to integrate this into communicator (which replaced OS call).

OS communicator when used in deskphone mode (ITP-5xxx, digital or analogue phones) requires OS link.

OS communicator when used in UC mode (SMT handsets) does NOT require OS Link

OS communicator when used in softphone mode does NOT require OS Link.

What is the error message displayed on communicator?

Since your software is 4.60 the whitelist option that Kaiser is talking about doesn't exist.