Please please first check the following:
- Are you on the most recent version of the app? We are constantly working on improving the app and if you are experiencing this issue, first check to see if you have the latest release as we hope it may be resolved.
- What is the state of your SD card? If your SD card is more than a couple of years old or came with your device, the SD card may be the problem. Old cards and ones that came stock in your device (often low quality mass produced) may be more susceptible to corruption and replacing them with a new SD card has often resolved issues.
To fix the problem, please go to the Settings menu in the app and choose the "Delete all content data" option. This will delete your database but will create a fresh database that will allow you to get into the content. You will have to reload your content but as long as you had synced your annotations, when you log in again, your bookmarks, highlights and notes will be restored.
Please note that this step can help fix a number of other issues in the app that you would often try to uninstall and reinstall the app for. Uninstalling usually doesn't help as the DB is not deleted. Please Delete all Content from the settings as a troubleshooting step rather than uninstalling the app.
As we are unable to track how often this issue may occur, if you have had this happen, please post a reploy to this post to let us know and if it has occured more than once, please let us know how often.