Remote Desktop Manager doesn't open after the splash screen.
This is due to an issue with the Remote Desktop Manager configuration file. The file is located in %localappdata% - Devolutions - RemoteDesktopManager and is called RemoteDesktopManager.cfg
You will need to move this file and reopen RDM, it will create a brand new configuration file.
You will have to re-register all of your data sources and point to either the file or database that you were using.