At 04:02am CST a registration/call management node in Frankfurt encountered an issue that resulted in failure of new registration from Clients and ICONs. As this node was linked to Lync Gateway in Amsterdam, calls from Skype For Business were failing. We have put Frankfurt Node in maintenance mode and routed Lync Gateway to another working node. Now registrations are getting redirected to another nearest node and SFB Calls are working fine. Sorry for the inconvenience caused.