Hey there, I just tried the non-pro version and it's working for me, so there might be an issue with the Pro version specifically.
Do you also have Play Store installed? If not, you need to install it, also make the calculator app was installed after sandboxed google play.
If it still doesn't work, go to settings > apps> find the app and select it and look for the "exploit protection compatibility mode" toggle in its settings, toggle that on and try again.