While iOS is a super cool update from iOS 12 to iOS 13, it has with it new and improved Privacy settings. One of these is any app's ability to access and use Bluetooth devices must now have permission granted, much like an app has to have your permission to access your location, etc.
If you just recently updated to iOS 13, you may get a notification asking you to allow mySugr to access Bluetooth. Be sure to tap "OK" to allow it if you'd like to continue importing data from your Accu-Chek meter.
Accidentally tapped "Don't Allow"? No need to worry! Just open your iPhone Settings then scroll down to the mySugr app. Then, switch the toggle for Bluetooth on (or green) so that the app can access your Bluetooth connections. You should now have the ability to import data from your Connected devices.
Let us know if you still continue to have trouble importing data from your meter after the iOS 13 update, and we'll be happy to go through some additional troubleshooting steps with you!