title: SQL Server 2014 can't login after detach database
body: <p>I'm using using Windows server and I'm having trouble logging in to SQL Server 2014.</p>
  
  <p>A few days ago I changed default user from master database to new one. But today I opened SQL Server Management Studio.</p>
  
  <p>I detach that database by right-clicking on it. After that, I disconnect from SQL Server Management Studio and then connect again.</p>
  
  <p>Check: Windows authentication</p>
  
  <p>Click OK</p>
  
  <p>I get an error:</p>
  
  <blockquote>
    <p>A connection was successfully established with the server, but then an error occurred during the login process. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.) (.Net SqlClient Data Provider) error:233</p>
  </blockquote>
  
  <p>When I try more to fixed it, now I get this error:</p>
  
  <blockquote>
    <p>Login Failed for user A. Reason: Server is in single user mode. Only one administrator can connect at this time (Microsoft SQL Server, Error: 18461)</p>
  </blockquote>
  
  <p>What causes this error and how do I login again and attach my database?
  Can I login to master database?</p>