SQL Server wont connect after DC demotion

I demoted a 2008r2 domain controller.  Now I cannot log into SQL server.  SQL was installed on this DC because at the time because this was there only server.  Made 2 Manage software runs on this server and the database for this software is installed on SQL.  I didn't realize that this would break SQL.  Anyone know any fix for this?  I won't be back to work until Tuesday to address this, but I an trying to research this now.  Hopefully I will have a fix for this by Tuesday to get our M2M software backup and running.
Michael McGuireSystems AdministratorAsked:
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I assume you can connect, but access is denied for the now nonexistent AD user.

You can start SQL server in single user mode, and add accounts or enable mixed mode authentication.
Starting SQL Server in single-user mode enables any member of the computer's local Administrators group to connect to the instance of SQL Server as a member of the sysadmin fixed server role.

If all else fails backup your .mdf and .ldf files and uninstall then reinstall SQL server.
Michael McGuireSystems AdministratorAuthor Commented:
Sorry I guess I should mention that this is SQL Server 2008 R2.  I actually have access to the SQL now if anyone is around and knows a solution.

Hiltop, the single user mode instructions on here say they are for 2017 and above.
Michael McGuireSystems AdministratorAuthor Commented:
So I have SQL fixed.  Hilltop you were right about the nonexistent user.  I was unable to get the single user mode to run, because the SQL Service would not run.  I did a repair of SQL Server and it added back the SQL Accounts that we lost because of the DC demotion.   I the went into  Local Security Policy and add the Local Admin user and group to the log in service.  I then went into The SQL Configuration Manager and restarted the SQL Service and Agent.  I was able to logon to SQL Studio Manager now and access the databases.
Michael McGuireSystems AdministratorAuthor Commented:
See above post

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