The alert wasn't a crash; it was a prompt. The app was trying to access a system folder it shouldn't have touched. The "crack" wasn't just unlocking the Pro features; it was attempting to inject a persistent background task.
If you choose to use an IPA file from an external source, you typically need a sideloading tool like AltStore or Sideloadly. These tools require a computer to sign the application with your developer certificate. Note that apps installed this way usually need to be refreshed every seven days unless you have a paid Apple Developer account. Better Alternatives for File Management
These versions often crash or fail to connect to network drives properly.
What I can offer instead is an informative essay on the broader ethical and security issues surrounding iOS app piracy, using this topic as a case study. Here is that essay: