Reported: after updating the RF Online 4.55 server from 0.1.x to 0.2.0, every character's inventory comes up empty, including a character created after the update.
Found: 0.2.0 added a per-item lock (the 4.55 item lock) and stores it in two new columns of the character item table. A database created by 0.1.x does not have those columns, and the 0.2.0 server does not add them to an existing database. So every read of the item table fails, for every character: the bag downloads empty, and a new character's starting items cannot be saved either. Bank storage reads fail the same way. The items from 0.1.x are still in the database; 0.2.0 cannot read them.
The RF servers are pre-release and support new installations only: a database carried over from an earlier version is not an upgrade path we support, so this is not something we will change.
What to do: stop the server, delete the game database it created, and start the server again. On the default setup that is the gommo_rf455 file in the server's db folder; keep gamedata_rf455, which ships with the bundle. On MySQL, drop the gommo_rf455 database and create it again empty. The server builds a new game database at startup. Characters and items from 0.1.x do not carry over; your account does, because accounts are kept in a separate database.