ssms does not let me change to server authentication mode and I can not log in I have been using SSMS and logging in through server authentication for a week now and yesterday when I tried to login it suddenly told me "no process on the other end of the pipe". 
I researched online and it said the problem is that the security property for the server is set to windows authentication and has to be changed to server authentication. So I log in to SSMS through windows authentication first to change it, however it said that I do not have permission to change the authentication mode, which is weird because I ran the SSMS as admin and it was on server authentication previously. 

Now I can not access my database at all as when I created the database it was under the SA account and it will just tell me I do not have permission to open the database or do anything basically. 

Also just for a side info the problem arised after I restarted my computer I believe, the server property is suddenly changed to windows authentication and I cannot log in through the SA account nor can I change it back to server authentication
Check this pinal dave solutions - https://blog.sqlauthority.com/2009/05/21/sql-server-fix-error-provider-named-pipes-provider-error-40-could-not-open-a-connection-to-sql-server-microsoft-sql-server-error/