Check the things Old-biscuit said.
Analog TVs were better at picking up distant signals than the new digital TVs are. With analog you could usually at least get a snowy picture. Digital is pretty much all or nothing. 40-50 miles may be out of range for your RV antenna depending on the terrain, even with a booster. However, there are typically a number of small market TV stations closer by and scattered outside of the large markets that you can typically get. You might try a portable antenna, if you have one, connected directly to the TV to see if you can get signal. That will at least tell you whether you have an antenna problem, or a signal strength/distance problem.