Most launcher errors can be solved by restarting your Shadow.
If you ever encounter any error codes or issues with starting your Shadow, please try shutting down your Shadow completely from the launcher. You can reach this by clicking on the help icon “?” at the top right corner. Select the “Shut Down Shadow” option and it will turn your Shadow off. Please wait about 5 to 10 minutes before starting Shadow again. It may take some time for Shadow to shut down if it has had difficulty starting. This will allow you to try and re-establish a fresh connection when starting.
Check out Help Center for a list of error messages and the information associated with each error code/message: https://help.shadow.tech/hc/en-gb/sections/360001048853--Error-Messages