Cannot reconfigure SEPM to new SQL server

Hi

I have moved SEP Manager database to a new server. When I then use Management Server Configuration Wizard to change database and try to save I get this error:

The management server "sepserver" already exists. You must change the server name.
And my new database server is not saved.

I have followed this tech note: https://support.symantec.com/en_US/article.TECH104723.html

It is step 7 that does not work for me:

Once complete, Run the "Management Server Configuration Wizard" and point
the Symantec Endpoint Protection Manager to the new server housing the newly attached Database.

How can I resolve this issue?

Windows 2012 R2
SQL 2014
SEPM: 12.1.6608.6300