The AP Inventory report is displaying APs in your current inventory of APs. If memory serves me right, that's APs that gave a sign of life (by sending statistics towards SCI) in the past 24 hours.
If the "problem AP" is a problem because it is... offline, for a while, then, it is the expected behaviour you'll not see it under AP inventory. If this is the cause, then there's no way to "refresh" this, essentially because the data is, in fact, refreshed already.
SCI is a reporting platform; I suggest that if an AP is misbehaving, looking it up in the controller might be a better idea.
If you want to try and find it anyways, you can try to do so by going to some other report (e.g. "AP Traffic"), and set the Reported Period to something that likely encompasses that AP (e.g. "Last 30 Days"). Then, try the AP filter to find this AP; If you do see it then, then likely the theory is correct (and, you'll see when the traffic graph ends, so you'll know when did it likely go offline)
By the way, if you're looking for where are your offline APs, you can utilize the Admin Monitor page (https://:8443
), under the "AP Group Sync", there's a link log of the last AP Group Sync. This log will contain a list of all zones, how many APs in them, and how many are in DISCONNECTED state (so you can use ctrl+f in your browser and search for "DISCONNECTED")
Hope this helps