The Transit Charts are 99 cents per chart for each date. For example, if you purchased a Transit Chart yesterday, then today you should still be able to view yesterday's chart. However, you would have to purchase today's Transit Chart to see the Transits for today.
If you purchased Transit Charts and they are not showing up, please send a screenshot of your Transit section. You should be able to access the last three Transit Charts you purchased by the date of the Transits if you go to your Transits section in your profile. There is an inherent limit for the number of transit charts generated in the iPhone app. They only save the last three Transit Charts. Any transit date that is different from one of the three will take the oldest one’s place on the list. To access transits you've purchased that aren't showing up in the list, just enter the same date and the system will recognize you've already purchased that date and shouldn't charge you to view it again.
We do offer Unlimited Transit Charts for $9.99 or the Pro App, which includes unlimited Transits and the other four features for a one-time price of $29.99. You can go to Settings>Upgrade if you are interested.