What Netweaver version needs the new ST-A/PI and what version of ST-A/PI did you download? I think you have the wrong component downloaded.
Example you downloaded a 7.0x version of ST-A/PI and the system EPS/In folder you placed it in is a 7.3 system, then SPAM shouldn't show anything as you don't have a valid 7.3 version of ST-A/PI.
Another thing to try, in SPAM display all support packs, then click the double up arrows on the sap gui menu bar within SPAM to collapse all the components, and verify the ST-A/PIs.