I have the same problem. App minimizes as soon as I try to open it. It works fine as a trial when I uninstall the key app.
It's been this way since the update to make it compatible with Android 7.0. I'm running stock OOS on OP3T rooted.
Hope it will be solved soon.
Thanks for the great app.
Edit: the app says 'the date of the device is wrong, please correct this' . But I am sure the date is correct.