We are using Pega CS 7.4

We have set up two Chat Server Configurations in Pega CS. Both Chat Server Configurations use the same Chat server hostname and port. But the Server configuration key is different. ( we have registered two different companies and using the private key of each company for each Chat Server Configurations in Pega CS ) When we define queues and assign skills for operators, the Chat Server Configuration can not be saved. It throws the below error.  Create Employee: URL paramter or Employee ID or one of the workgroups ID is not valid{"error":{"message":"","type":"request_failed","param":null,"rawError":"error: null value in column \"max_chats\" violates not-null constraint"}}

When we remove skills from the operators and when there are no operators assigned to any of the chat queues, the Chat Server Configuration instance can be saved without any issue. 

Any idea why this is happening?