I tested it now and it seems config backup does not work when hotsync is installed.
If you do a config backup on a hotsync system there is no error but no backup. Could it be you restored an old backup (maybe the first automatic one after initial configuration)?
I assume hotsync syncs the master config backup to the slave so it is not allowed to overwrite it. (or it’s a bug?)
AFAIK the config restore process restores the complete configuration in any case (no matter if done in first config wizard or manually afterwards).