The Information tool in Portal may not always display the selected feature attribute information resulting in the information box being blank.
The information tool seems to work spordicaly and dependant on zoom level
The situation may be where the click is not close enough to the feature for the info tool. It can be tricky to click on the feature itself.
You can control the size of the buffer by adding <add key="Intergraph.WebSolutions.Core.SDIPortal.MapPublisher.FeatureInfoBboxBuffer" value="10" /> for example in the portal web.config.
It creates a buffer in pixels around the point you have selected (the default being 3 pixels) and brings up the attributes of all the features in that area.