If the server list has not been checked at the beginning of the update (see Preparing the Update) and there have been more servers registered in the database than actually running, it might be the case that there is a server within the HA network that did not reconnect to the productive database.
In this case, you have to switch over the data source manually to the productive database.
The database schema will be renewed the first time an updated server connects to the productive database. Afterwards, all other servers within the network can be switched over to this database.