Thanks for the quick reply. However authentication was 'on' (with unsername and password) on the server."read only authentication" : disabled on server.
I have noticed that some changes made on client have been done on server, but others not. Changes on client remained unchanged on client and server after next day MC launch.
Does it mean that changes made on client must be confirmed by the refresh button on the client ?
On the client, if you look in the media network section of the options menu, there is a heading "Client Options." Make sure that the "auto-sync" box is checked, and the client should then sync changes back to the server automatically. One thing to know though is that there are just a few specific kinds of changes that cannot be made on the client. For example, cover art has to be changed on the server, not the client and any client changes to cover art will not be synced. Similarly, changes to file locations or filenames cannot be usefully done on the client.
But almost all other tag changes, etc. can be done on the client and should automatically sync back to the server if the auto-sync box is checked and the client has an authenticated connection to the server.