Hi there! I understand you're seeing an error 500 with the message "data format returned by server is wrong" when trying to save data in the iHealth MyVitals app. Let's get this sorted out together.

First, just to clarify a bit: Is this happening when you try to save data from a particular device or after entering some readings manually? Also, are you using the app on your Windows machine's browser or a mobile app? This will help me tailor the steps better.

Meanwhile, here’s what we can try:

1. Check Your Internet Connection: A flaky connection can sometimes cause server communication issues. Make sure your connection is stable.

2. Clear Browser Cache and Cookies: Since you are on Windows with a WebKit-based browser, clearing cached data can fix problems caused by corrupted or outdated files.
- Go to your browser settings.
- Find the section to clear browsing data.
- Clear cache and cookies, then restart the browser.

3. Update the App or Browser: If you’re using the web version, ensure your browser is up to date. For the mobile app, update it via the appropriate store.

4. Try a Different Browser or Device: See if saving data works from another browser or device to isolate if the issue is browser-specific.

5. Log Out and Back In: Sometimes, session errors cause this. Logging out and logging back into your account might help.

6. Check for Server Issues: Error 500 indicates a server-side problem. This might be temporary, so waiting a bit and trying again can help.

7. Advanced Step - Check Data Input: If you are manually entering data, make sure it is in the correct format (e.g., correct units, no extra characters). Sometimes, invalid input data can cause this error.

If after these steps the issue persists, please let me know which steps you have tried and any extra details, like what device model and version of the app you’re using. I’m here to help you get this fixed!