When you change the name of your server which is running SQL, you should also make sure that SQL gets updated with this new name. Proceed with the following procedure:

• execute the command: select @@servername
  this command will return the current servername stored in SQL
• execute the command: sp_dropserver ‘servername‘
  in which servername is the name that you got from the previous step
• execute the command: sp_addserver ‘new servername’
• restart the “ sql server”  service and the “ sql server agent” service
• execute the command: select @@servername
  to verify everything went just fine