Lync: “Cant sign in to Lync – There was a problem acquiring a personal certificate required to sign in”

Remember the other day when I wrote about this Lync Error Message? So today I had to deal with another problem regarding Lync (they just keep coming!).

One of my colleagues had a problem signing in to Lync. To make it more interesting – other users could log in on the same machine, and the user could log in on other machine, but couldn’t get to log in on her own computer (Windows 8.1).

The Problem

Whenever she tries to log in to Lync, she gets the following error message:

“Cant sign in to Lync – There was a problem acquiring a personal certificate required to sign in. If the problem continues, please contact your support team”.

Lucky her – I’m the support – one man – team 🙂

The Solution

First of all I must tell you – I already tried to repair Office 365, and already tried to uninstall and reinstall the software. It’s not going to help you.

There are a couple of solutions here. If one doesn’t work for you – keep going and try the next one.

Solution 1

Open Lync login window, and click on “delete my sign-in info”. Then – type in the login details and password again and try to log in.

Solution 2

Clear Lync’s cache:

1. Go to “C:\Users\Username\Appdata\Local\Microsoft\Office\15.0\Lync\” and delete the specific user’s sip (Session Initiation Protocol) folder.
2. Go to “C:\Users\Username\Appdata\Local\Microsoft\Office\15.0\Lync\ Tracing\” and Delete All files. DO NOT DELETE ANY FOLDER.
3. Open the registry editor (Start + R -> type regedit -> Enter), go to “HKEY_CURRENT_USER\Software\Microsoft\office\15.0\Lync” and delete the specific user’s expandable sip profile folder (the one that contains the user’s email address to sign in to Lync):

Solution 3

This is what worked for me, after 2 hours of researching.

As part of clearing Lync’s cache, we also need to delete the RSA (encryption key). In order to do that:

1. Exit Lync.
2. Go to “C:\Users\user\AppData\Roaming\Microsoft\Crypto\RSA.
3. You’ll see one or many folders (defends on how many users logged in to their account on the computer). Delete all the folders.

4. Try to log in.

Don’t forget that if you delete all the folders, each and every user will have to sign in again.