We already spend 14 houts straight trying to solve this issue:

Chats are being initiated, but customers do NOT receive the messages from the agents.

All our support team members could not work this weekend.
Happened out of no where after restarting the WIN2012 server

 

who has an idea, as it is kind of pressing! Thank you in advance

 

=====================
[2017-04-08 10:37:05 PM]
ManagementUser didn't exist on KeepAlive: Cookie=[null]

=====================
[2017-04-08 10:37:16 PM]
Could not get current user
Object reference not set to an instance of an object.
System.NullReferenceException: Object reference not set to an instance of an object.
   at SmarterTrack.HelperClasses.Security.ManagementUserInfo.GetCurrentUser(HttpContext context)