SQL Server connection problems

SqlserverConnection problems

 

The connection is normal before, and then I don't know how it works. The error is as follows:

 

Enterprise ManagerConnection:

Use"."AndIPAddresses can be connected

The machine name cannot be connected.,The following error is reported:

Query AnalyzerConnection

UseIPThe connection is normal.

Use "."The following error is reported:

 

The following error is reported when the server name is used:

Who knows why ??? Thank you!