Hi! I see you're having trouble with the camera flash not coming on when using the Welltory app. Let’s make sure we get your flash working properly for the measurements.

Could you please tell me:
- Are you using the back camera for the measurements?
- Does your phone’s flashlight work outside the app (like in the regular camera app or quick settings)?
- Has this issue started recently, or has the flash never worked with the Welltory app on your device?

Meanwhile, here are some step-by-step things we can try:

1. Check camera permissions:
- Open your phone Settings > Apps > Welltory > Permissions.
- Ensure the app permission for Camera and Flashlight is allowed.

2. Proper finger placement:
When taking measurements, place the tip of your finger gently on the camera lens and partly cover the flash with your finger. It’s recommended that the finger tip sits near or on the flash to illuminate properly, but not too hard or fully blocking it. The flash helps the camera detect blood flow changes.

3. Close background apps and restart your phone:
Sometimes other apps might be using the camera or the flash. Restarting the device can reset this.

4. Update or reinstall the Welltory app:
Make sure your app is up to date from Google Play Store. If the flash is still not working, try uninstalling and reinstalling the app to reset permissions and background processes.

5. Avoid low power mode or battery saver:
Battery saver might disable the flashlight. Ensure it’s off while taking measurements.

6. Check for physical flash issues:
Test your phone’s flashlight outside the app (e.g., in the regular camera app or the quick settings flashlight toggle). If it doesn’t turn on, the problem might be with your device hardware.

If you’ve tried these and it’s still not working, let me know what you tried and if you see any error messages. We can then dig deeper or escalate if needed.

Are you satisfied with this initial troubleshooting? I’m here to help you get it working smoothly!