Fix: Skype for business error: There was a problem acquiring a personal certificate to sign in

How to fix Skype for business error: "There was a problem acquiring a personal certificate to sign in"

Step 1: Delete sign in information

• open skype
• click Delete my sign-in information
• re-login

Step 2: Delete certificate

• open a command prompt and run the following command:
• certmgr.msc
• Go to Personal/Certificates
• delete the certificate issued by Communications Server

Step 3: Flush the DNS cache

• open a command prompt and run the following command
• ipconfig /flushdns

Step 4: Delete sip folder

• delete your sip folder:
• Windows XP
• go to %USERPROFILE%\Local Settings\Application Data\Microsoft\Communicator<sip_YourEmailAddress>\
• Windows Vista/7/8/10
• go to %LOCALAPPDATA%\Microsoft\Communicator<sip_YourEmailAddress>\
• if you can't find the folder just search in %appdata% for SIP_ and delete that folder (it should look like this: sip_YourEmailAddress)