To add to the comment of @Nighthawk it might be a SIM card Issue. Have you tried removing and replacing the SIM?
Remember, the Travel Pass only nets you a cheaper price for your calls, texts and data, it does not change how your phone works.
So your phone says No Service instead of showing signal strength? That could be something in the area or the phone itself. Did your phone show another local provider that was in use? There should be a couple providing coverage in that area.