Hello,
Before going any further, is this the error you are experiencing?
[Bug] Subscribe instead of Start-Button - Getting Started & Setup - Epic Developer Community Forums
If not, I have a few questions. How far into the launcher do you get before it fails? Can you log in? Does the crash reporter appear? Please go into the logs folder, if it was created, and post the log file from there if possible. It is located here: C:\Users\AppData\Local\UnrealEngineLauncher\Saved\Logs
If you can attempt to launch a project, but it fails then, please go to that project’s logs and post the log from the failure. Those logs are located in: [Project Name]/Saved/Logs
Thank you for your report.