v3.21, all servers unusable after restart

I updated RDM from version 3.12 to 3.21; I created a new .rdm file and deleted/recreated the folder in %AppData%. I re-entered all servers and re-saved the credentials. Despite this, the connections only work as long as RDM is running. If I close and restart the application, all connections report "disconnected," and no further connections can be established. Every single server has to be re-entered, and again, it only works for the duration of the current RDM session.
Has anyone encountered this? Does anyone have any advice?