This article is to reset unknown password for SA account
1. Go to SSMS. Use Windows Authentication and login as Administrator
2. Expand Security > Logins then Locate SA account. Right click on SA then go to properties
3. Input new password then click OK
4. Go to Status then on Login click Enabled
5. Server Roles should just be default with sysadmin roles
6. Right click on the server name then go to server properties and make sure that SQL Server and Windows Authentication mode is enabled then click OK
7. You will be prompted to restart the SQL Server. To do this, Right click again on the server name then click restart
8. Login again using the SA account to validate