I have a very similar issue.

I am developing a monitoring tool,

And there is an incident I cannot monitor.

One of my users logged into an application to insert data into the database.

I can see his machine name, but I cannot see his name.

His login_name shows S-1-9-3-322691058-1310504681-3474585482-2036716736.

This comes from sys.dm_exec_sessions login_name column.

I am looking for a way to find the user name, if I find something I will post it here.

I have tried many ways from inside SQL Server.

select * from sys.server_principals

where sid = 'S-1-9-3-322691058-1310504681-3474585482-2036716736'

select suser_name(S-1-9-3-322691058-1310504681-3474585482-2036716736)

--select suser_name()

sp_helplogins

SELECT * FROM master.dbo.sysusers

where sid = 'S-1-9-3-322691058-1310504681-3474585482-2036716736'

SELECT * FROM master.dbo.syslogins

where sid = 'S-1-9-3-322691058-1310504681-3474585482-2036716736'