Suspect a few people aren’t sure the best way to do this so:
- Close Zwift completely, including the launcher from the system tray (right-click and Exit).
- Hit Start and type Internet Options and select it.
- Down the bottom under Browsing History hit Delete…
- Tick all the boxes except the first one and press Delete.
- OK out of Internet Options.
- Start Zwift and try again. You’ll need to log into the launcher again because you’ve now deleted your credentials.