If the Fitdays app is only displaying weight and BMI, there are a number of troubleshooting steps you can follow to resolve the issue and ensure that all parameters are shown.

1. Check Bluetooth Connection:
Ensure your device is properly connected to your scale via Bluetooth. Disconnect and reconnect the device. Sometimes resetting the connection can resolve display issues - learn more.

2. Restart the App:
Completely close the Fitdays app and then reopen it. This can refresh the data feed and might make all parameters visible.

3. Calibration and Setup:
Verify that the scale has been calibrated and set up correctly according to the instructions provided within the app or in its manual. Incorrect setup might lead to limited data being displayed - learn more.

4. Update the App:
Check if there is a new version of the Fitdays app available. Outdated apps may experience functionality issues. Update the app through your device’s app store.

5. Permissions Check:
Go to your device settings and ensure that Fitdays has the necessary permissions to access necessary data such as health and fitness parameters. This may include permissions to access your health monitoring features.

6. Delete Cache:
If you are using an Android device, consider clearing the cache for the Fitdays app. This can help eliminate any temporary issues affecting data display - learn more.

7. Consult the FAQ:
For specific guidance related to parameter visibility, refer to the Fitdays FAQ page. It contains insights on troubleshooting display issues - learn more.

8. Contact Support:
If none of the above steps resolve the issue, it may be necessary to contact Fitdays customer support for further assistance.

By following these steps, you should be able to resolve the matter of the Fitdays app not showing all the parameters.