Make sure your Tally is open with the company loaded.
Check ODBC Port, see the highlighted area.
If you are not able to see the server with ODBC like above then, click on this area and you will see something like below.
Click on advanced configuration.
Now change the top 3 fields to both, yes and port number of your choice(should be in 9000 - 10000).
If the port appears on restart of Tally on the Gateway fo Tally then the ODBC server has been configured.
Now open the Desktop Application, log in, and go to settings.
Enter IP and port where ODBC Server of tally is enabled.
If Tally and Desktop application are on the same system, IP would be http://localhost and port would be what you configured in Tally.
This is how your window should appear after the configurations.
NOTE: Mention your Username, Phone number, and organization with the relevant query (E.g. I need help with Tally Syncing. I am on a multi-user license.)