As others have indicated, you've probably got the wrong source selected. (i.e. your TV is looking for a signal from a non-existent DVD player, set-top box or similar).
The 'Source' button on many remote controls is indicated by a rounded rectangle with an arrow pointing into it. If you've got such a button (or perhaps one labelled 'Src' or similar) press it. Then use the up/down buttons to select the 'normal TV' source. (It's commonly labelled 'DTV' but it might also be labelled 'TV', 'Aerial', 'Ae', 'Antenna', 'Ant', 'RF' or something else). Press the 'OK' button to accept that source.