Hi,
usually MapStore on layer add from the catalog, queries the DescribeLayer of GeoServer to guess if there is a WFS service associated to that layer.
If Ok, it saves the URL of the WFS service in the map object.
If this WFS url is present, the tools reserved to vector data are show (feature grid, widgets...).
I don't know the reason of this to fail, but you may look at the requests done on layer add to guess what's going wrong.