1. If you log out from the application then you need to scan the smart scale again. Check whether your smart scale is paired with your device or not. Kindly go to settings > scan devices 

2. Check your internet connection while taking measurement. if progress bar runs endlessly then reset your wifi / mobile data and select the user profile again and stand on the smart scale for measurement. 

3. If you are using the latest mobile phone (android pie and above) then for Actofit smart scale app select  don't optimize battery option from settings. (settings > Battery > select Actofit smart scale > select Don't optimize battery) 

4. set background limit from settings to allow background processes. (go to settings > search background process > set standard limit)  

5. Click on back button on measuring screen . Then go to change user option and select your profile again. And clicked on measure now button and then stand on the smartscale.