@Angle: Please can you confirm the model number and current Android version of the device you're attempting to access S Health on? In the meantime, try searching for an update for the app via the Google Play Store > Tap the 3 lines in the top left > My Apps & Games > Updates. Also, if you connect to Wi-Fi or Mobile Data when you open the app, are you able to proceed? I'd also recommend heading to Settings > Apps > Samsung Health > Storage > Clear Cache, then restart your device, to see if this helps.
