How does the trial system work?
When you install our app for the first time, you can use it free of charge for a period of time (the trial period).
The trial period can be enjoyed only once for each store. If the trial period were available every time the app is installed, a store could uninstall and re-install the app many times to use the app forever.
We are following the trial system suggested in the Shopify documentation at https://help.shopify.com/api/app-store/charging-for-your-app/faq#does-uninstalling-and-reinstalling-my-app-reset-the-free-trial
When the app is installed in the store for the first time the trial period starts. The trial period finishes at a specific date (30 days after the installation), no matter whether the app was removed from the store or not.
If you don't want to be charged when the trial period expires, you have to uninstall the app before that date.
The Full Page Zoom app has a trial period of 30 days. You can re-install the app any number of times within those 30 days and you will not be charged.
On the other hand, if you uninstall the app and install it again after the trial period, you will be charged immediately.