This is standard code. Alright. Well you can open Item card even if you have permission only on item card and item table. I really can’t tell what is wrong with your case.?
My guess is that you are using your customer license to work in a Cronus database, and you are trying to look at an Item that has quantities on a service invoice line. The Item card tries to display the “Quantity on Service Order” flowfield (which causes it to try to read from it) and you get the error.
Load the cronus license, remove all the data from that table and you should be able to open it with your license. The other way would be to remove the “Quantity on Service Order” field from the Item Card.
Daniel suggestion is the most likely but if not this could also cause the problem is there is old value entries generated from service invoice / credit.