If you recently performed maintenance on your Microsoft Lync servers, including patching, Lync may experience an error that the server cannot validate the certificate.
Can’t Sign in to Lync
The server cannot validate the certificate. Please try again later. If the problem continues, contact your support team.
The error is most likely related to the Lync certificate not using standard cryptography settings. You can easily get around the error by selecting delete my sign-in info.
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