Hi there! I see you're having trouble logging into the Lufthansa app with the error code 99998, and you've already tried several suggestions. Let's get to the bottom of this together.

Just to clarify first:
- Are you using the latest version of the Lufthansa app installed on your device?
- Have you tried clearing the app cache or reinstalling it?
- Is the error appearing right after entering your login details, or at some other point?

Once I have a bit more detail, I can guide you through the next best steps. Meanwhile, here's a step-by-step approach that usually helps with this error:

1. Check App Version and Update if Needed
Sometimes login errors occur due to outdated app versions. Please go to the Microsoft Store on your Windows device, check for any updates for the Lufthansa app, and install them.

2. Clear App Cache and Data
This can resolve issues caused by corrupted temporary files:
- Close the Lufthansa app.
- Open Settings > Apps > Lufthansa app.
- Click on Storage.
- Select "Clear Cache" and then "Clear Data".
- Restart the app and try to log in again.

3. Reinstall the App
If clearing cache/data doesn't help, uninstall the app fully, then download and reinstall it fresh from the Microsoft Store.

4. Check Network Connection and Firewall Settings
Ensure your internet connection is stable and that nothing (like firewall or antivirus software) is blocking the app’s access to the servers.

5. Try Logging In on Another Device or Web Browser
This helps identify if the problem is device-specific or an account/server issue.

If after these steps the issue persists, the error code 99998 might indicate a backend or account-related problem on Lufthansa’s side requiring higher-level support intervention. In that case, you may want to contact the Lufthansa mobile services support at [email protected] with the error code and details you provided here.

Let me know if you want me to walk you through any of these steps, or if you have more info about when the error appears. Together we’ll get you logged in!

Are you satisfied with this initial guidance?