PostgreSQL + why archive_command line is marked after barman restore
As far as barman knows, you did the restore in order to make a clone of your instance and the original instance is still running someplace.  You definitely don't want two instances sending WAL to the same archive.  If you are dead certain the original instance has been irreversibly destroyed, then you should turn archiving back on.  Otherwise, you should start archiving to a different location.