Can’t open the cart:
There is a button that normally says, "Unlock Narc Drawer". If that says, "Unlock Cart" the cart is connected but it didn’t respond to the unlock command.
The other possibility is that the computer did not connect to the cart. Please check both ends of the serial cable. Maybe even a different Serial port on the computer.
Then please close Pharmacy Touch (so there is no login screen) and re-open it and try again.