I have the same problem, after clean install Sierra with ICash.
When I download and setup was no problem but when I try to run application it says "ICash can't be open"
What problem can be? How can I solve that?
I, too, have been unable to print from an otherwise working version of iCash in Sierra, only to now not be able to even open the app and see or make entries after downloading the claimed fixed version today. I have an open support ticket about this.
I'm becoming concerned to the point of investigating an alternative application. Another option I'm considering is digging out a recently retired pre-sierra imac just to run iCash until this is solved. I'll have to do something soon!
This is a Sierra Gatekeeper issue. Not sure where it comes from, duplicate apps? Not sure. A good solution could be to remove previous application first and then download the new one. Anyway, did you know you can simply right-click on the iCash icon and select 'Open'? That will bypass Gatekeeper.
Current iCash version is properly signed, our developer signature is up-to-date, everything has been verified. However around 4 iCash users have this problem again and again and again whatever I do. That started the very same day Apple released Sierra.