Question re Call Center and Business Object

Hello ​@RutJWhalen 

Have you managed successfully to connect invoice objects to case?
We are struggling with a similar problem and although it is possible to select business object “invoice” on the case basic data setup:

I am not able to select if still from the list on the case:

But if I try to set up “Attach LOV Order” system is popping out an error telling the opposite (it is not possible):
 

Have you find out by any chance is it possible?

Thank you so much in advance for sharing any insights.

Best regards,
Kasia