This is down to a Security Profile permission within FinOps Administrator.
In order to see the Edit button on the POP: Receive Goods screen you must be in a Security Profile with the right permissions.
The correct profile permission setting is called Allow Editing of Open Order Lines.
In order to check and enable (or disable) this permission:
In a web browser navigate to the FinOps Admin Remote Gateway
Log in to the remote gateway with your Hosting.Admin credentials
Open FinOps Admin and log in to the correct SQL Database
Click System Options, Security Profiles, select the correct profile and click Edit
On the Security tab, on the left, double-click the Purchasing ... folder icon
Click Receive Goods Options
On the right, against Allow Editing of Open Order Lines, either enable (green tick) or disable (red cross), click to change the setting.
Click OK to save changes.
Ask the user to sign out and sign back in for this change to take effect.