How to Resolve SA logging error of SSMS

1.Open Services and Make sure these services are set to automatic start

If any service is Stopped then go to properties and mark its startup type as Automatic and then restart SQL Server(Your server name ) service.

2. Log in to Windows Authentications first

3. Go to Server properties >> Security and choose SQL Server and Windows Authentication Mode

4. Go to SA Properties and Untick "Enforce Password Policy" and choose any one letter password 

5. Go to Status Tab and Enable SA Login and Permission 

6. Restart the SQL Server Service done in Step 1.

Now Login to SA using the password you set.

Done !!!