Try these checks in order:
- Confirm whether the Microsoft account works outside the launcher. Sign in in a browser first. If the account cannot sign in there either, use the Microsoft account Sign-in Helper.
- Make sure the same Microsoft account is being used everywhere the launcher depends on. Check that Minecraft Launcher, Microsoft Store, and Xbox app are all signed in with the same Microsoft account. A mismatch between these apps is a common cause of launcher sign-in failures.
- Repair or reset the Minecraft Launcher. On Windows, open Settings > Apps > Installed apps > Minecraft Launcher > Advanced options > Repair. If Repair does not help, use Reset.
- Restart the PC. Restarting can clear temporary sign-in issues.
- If Windows sign-in problems also appear on the PC, try Safe Mode with Networking. From the sign-in screen, hold Shift while selecting Power > Restart, then go to Troubleshoot > Advanced options > Startup Settings > Restart, and select 5 or press F5 for Safe Mode with Networking. If sign-in works there, the issue is likely not caused by basic drivers or default settings.
- If the problem happens only with one Windows user profile on that laptop, test with a new local Windows account. Go to Settings > Accounts > Other users > Add account > I don’t have this person’s sign-in info > Add a user without a Microsoft account. Sign in to that new Windows account, then open Microsoft Store or Minecraft Launcher and try the Microsoft sign-in again. If it works there, the original Windows profile is likely corrupted.
If the Microsoft account itself is not recognized anymore, or shows account-not-found errors, use the Sign-in Helper tool.