When you replicated the entry via FB01 or FB50, did you enter the tax code? Make sure you run one example with tax code & another one without, and you will see the difference. Generally, the tax info icon displays the tax data for a given transaction such as tax amount, tax rates, etc. If a document does not contain any tax relevant info, then you won't see this tax info button.
Are you certain that you entered the transaction with GL accounts that are relevant to taxes & entered the tax codes on the line items? If the GL accounts are not relevant to taxes, you will not be prompted to enter taxes & therefore the tax info will not be displayed.