cannot sign into communicator because your
computer clock is not setup correctly !!!
This issue arise when lync server's directory control (DC) clock time is not match up with Lync Client's pc clock time.
The easy solution is that to make sure that the Lync DC system time is maximum 5 minute different then Client's PC time.
The smart solution is --
STEP 1. Goto client pc's adjust date and time.
STEP 2. Then on Date and Time window select Internet Time tab.
STEP 4. On Server text field set the Lync DC / active directory IP address and click update now .
STEP 5. Now you will get DC system time and set it by clicking OK.
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