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Lync 2010 Personal Certificate Problem on Login

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Good Morning,


I have recently started a trial of Office 365, all is well apart from this issue with Lync 2010.


On any PC i have tried so far, I cannot sign in to Lync 2010 with the one default account.


Error Message:

"Cannot sign in to Lync

There was a problem acquiring a personal certificate required to sign in. If the problem continues, contact your support team."


I have downloaded and re-installed Lync 2010 and Office Desktop Apps Setup multiple times now, along with updating the Windows update for Lync 2010 when the Desktop Apps finished installing.


I removed the EndpointConfiguration.cache file before a few sign in attempts.

Followed this KB article advising to delete any certificates or crypto RSA key container i do no currently have. Last but not least i checked credential manager for any incorrect saved details, nothing to remove there.


Really at a loss with something that appeared so simple upon sign up.


Can anyone help ?


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  • Hi HCS Matt,

    I am glad to hear that everything is working. It was a pleasure helping you and have a great day.

    Brent Coldewey

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  • My company has federated our Active Directory with Office 365 and have intermittent and widespread occurrences of the "There was a problem acquiring a personal certificate required to sign in. If the problem continues, please contact your support team." error. We have had an open ticket with Microsoft Support for over two months with no resolution.

    We have tried the troubleshooting steps covered in as well as reinstalling the latest versions of Lync and the Microsoft Online Services Sign-In Assistant. I have supplied Microsoft with numerous network trace and MOSDAL (Microsoft Online Services Diagnostics and Logging) logs.

    The only consistent workaround we have found is to have the user visit an Office 365 service (e.g. Outlook Web Application, SharePoint Online) and authenticate. Once the user accesses Office 365 through the web browser the error disappears and the user is able to sign on to Lync.

    It appears to be a defect with the design and/or individual Microsoft products and services. Based on our overall experience with Office 365 we feel it is a beta product.

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  • I have also found you cannot connect an Office 365 email account to an outlook client until it has signed in once on the OWA.

    Providing an extra step to do before giving out details to users or making it a VERY clear point in documentation for the user to do first or support tickets get logged.

    It seems good advice to log into the OWA as the user first before rolling out any of the software or attempting any logins i've found.

    Overall Office365 seems to free up having an AD and exchange server on some client sites where you really don't need one.

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