Hello Marc, and welcome to the community!
Did you put your passwords in to an org’s vault? Recent BW update “disappeared” org’s passwords that are not assigned to a collection, and can now only be accessed from the admin panel. The 3.1 web vault supposedly includes a tool ( Collections | Bitwarden Help Center ) to assign these passwords en masse into a collection.
(edited: You can only export unassigned org’s items from the web client.)