Why am I unable to see features of layers that are checked on in the table of contents?

Web Map Service (WMS) and Web Feature Service (WFS) servers often host data that is only visible at certain scales. There are situations where ArcMap does not know a layer’s visible scale range. If the scale range is unknown, the layer’s visibility checkbox is checked and not grayed out in the table of contents, but the layer only displays on the map when the map is zoomed to a valid scale. Either zoom around the map until the layer in question displays, or contact the service provider to obtain the visible scale ranges.