Troubleshooting Skype for Business/Lync Secure Chat And Conferencing

While logging in to Lync client user may face on of the following errors:

Cannot sign in because server is temporary unavailable

Can’t sign in to Lync. We’re having trouble connecting to the server

Lync was unable to sign in. Please verify your logon credentials and try again

Find the troubleshooting steps below:

Error: Cannot sign in because server is temporary unavailable.

Resolution:

• Verify user has Lync service enabled. To check this navigate to HostPilot”® Control Panel > Services > Skype for Business > verify that box next to user’s name is checked.
• Verify the settings are correct: under Tools > Options > Advanced (OSX: Advanced) both internal and external servers are set up. You may find correct server addresses in HostPilot under Services > Skype for Business > Instructions > Server Name: lyncsip.exchXXX.serverdata.net.

Error: Can’t sign in to Lync. We’re having trouble connecting to the server.

Resolution:

• Verify the settings are correct: under Tools > Options > Advanced (OSX: Advanced) both internal and external servers are set up. You may find correct server addresses in HostPilot under Services > Skype for Business > Instructions > Server Name: lyncsip.exchXXX.serverdata.net.
• Run Trace Route to Lync server. Read the Knowledge Base article on What Is A Trace Route (tracert)? How Do I Run One?. You may find correct server addresses in HostPilot under Services > Skype for Business > Instructions > Server Name: lyncsip.exchXXX.serverdata.net. If there are some asterisks (*) or the response time is > 200 ms, locate the hop where it happens. You may need to reboot your router or modem or contact your ISP. If the asterisks appear beyond your Network, contact Support.
• Check Lync ports and protocol are open and supported in your network. Read the Knowledge Base article on Ports And Protocols Used By Skype for Business/Lync Secure Chat And Conferencing.
• Replicate connection in different environment (different machine and network). If user is still not able to login contact support.
• If different machine/network worked, test with another network and another user on the same machine (e.g. connect machine to Wi-Fi).   If users are able to connect through different network, contact your local Network Administrator to resolve router/firewall/network configuration issues. If another user is not able to connect as well, contact your local administrator to resolve Windows/OSX core issues.

Error: Lync was unable to sign in. Please verify your logon credentials and try again.

Resolution: 

• Verify you are using correct username and password and are able to login to https://exchange.intermedia.net/ControlPanel/Login?ClientType=WebMail.
• Verify you are using mailbox UPN (not an alias). You may find correct UPN in HostPilot under Users.
• If you have recently changed UPN for user, SIP address and SIP attributes may not match new UPN. Contact support for resolution.
• Clear up Lync cache: 

Lync 2010 or 2013 for Windows

1. Log out of Lync.
2. Delete any sign-in info.
3. Exit Lync.
4. Open Run bar and type in \%AppData%\..\Local\Microsoft\Office\15.0\Lync\ for Lync 2013, or  \%AppData%\..\Local\Microsoft\Office\12.0\Lync\  for Lync 2010.
5. Delete sip_profileName folder.
6. Delete all files in Tracing folder. Do not delete the folder itself.
7. Clear DNS cache: in Command Prompt run ipconfig/flushdns command.

Lync 2011 for MAC

1. Log out and quit Lync.
2. Go to Finder > press Command+Shift+G > type in /users/<MacUsername>/library > delete the following files:
   • Caches > com.microsoft.Lync
   • Internet Plug-Ins > MeetingJoinPlugin.plugin
   • Keychains > all files beginning with OC__KeyContainer
   • Logs > Microsoft-Lync-x.log and Microsoft-Lync.log
   • Preferences > com.microsoft.Lync.plist
   • Preferences > ByHost > MicrosoftLyncRegistrationDB.xxxx.plist
3. Go to Finder > press Command+Shift+G > type in /users/<MacUsername>/documents > navigate to Microsoft User Data > delete the following folders: Microsoft Lync Data and Microsoft Lync History.
4. Open Keychain Access from /Applications/Utilities folder.
5. Delete all keychains starting with OC__KeyContainer.
6. In your Login keychain, delete all e-mail address certificates.
7. Empty Trash.

• Modify the following Registry entry: HKEY_CURRENT_USER\Software\Microsoft\Shared\UcClient:
  • Set ServerSipUri to a string value of the user’s SIP proxy address
  • Set ConfigurationMode to a dword value of 0
  • Delete the ServerAddressInternal string
  • Delete the ServerAddressExternal string
  • Delete the ServerUserName string
  • Restart PC.

Note: to open Registry on Windows Vista/7/8: Start > type in regedit in Search field.

• Reset Lync Client Preferences to default. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Communicator and delete this entry.

Note: to open Registry on Windows Vista/7/8: Start > type in regedit in Search field.

Ref: https://kb.intermedia.net/Article/3216##Error1