I am trying to learn Sage 50 quantum Accounting... I have 2023 edition. 
When I try to create an Invoice, I can add a product (that has quantity on hand) to the invoice.

But, when I try to enter a price or quantity, I can't type anything in the boxes.  Doesn't work in Quote, Sales Order, OR in Invoice creation.

It does nothing... it ignores anything I type and the boxes stay empty.