This is a problem we hear about from time to time but have never duplicated in-house so we can't really research it in detail.
When we have examined our server logs to try to identify the problem, we have found that the request for the book never makes it to our server. Something is happening on the user's end that is keeping the request from getting to us. Often, the app has worked in the past and we know it works for others, so we don't think it's anything the app itself is doing. We think it's something in Windows that keeps the program from being able to communicate with our server.
We believe this happens most frequently when Windows is downloading updates in the background. We believe it manipulates folders and permissions during that time, and that it confuses PocketBible for some reason. This suggests that simply waiting a while will allow it to start working, and that the suggestions below are really just keeping you busy while Windows finishes its updates.
Some users tell us it started working again after they reboot or after Windows installs an update. So try rebooting. If that doesn't work, check for Windows updates and install any that might be pending. If none of this works, remove the app, reboot, and install the app again. Some combination of these actions will usually get it working again.
Sorry we can't be more specific but this appears to be a Windows issue so we don't have much control over it. PocketBible will work once Windows is working.