# Troubleshooting

Use these checks to resolve common Offline Maps issues, including delayed download failures, Swift error handling, missing map data, and offline startup behavior.

**The enqueue completion returned nil, but the download failed later**

A nil completion error only means that the task was enqueued. Network transfer, decompression, and installation happen afterward. Read the final result from the progress listener.

**Swift does not allow `progress.error.code`**

Most likely the _Objective-C NSError_ property is imported as `Error?`.

Convert it first:

```swift
let nsError = error as NSError
```

Then read `nsError.domain`, `nsError.code`, and `nsError.userInfo`.

**The downloaded region does not appear on the map**

Verify that:

1.  The download state is `.completed`.
    
2.  The map uses and registers a style from _NGLRegionalOfflineStyleCatalog_.
    
3.  The map engine is refreshed after returning from the download page.
    
4.  The active tile server is TomTom instead of any other provider.
    

**The first download cannot start while offline**

The first use requires connectivity to prepare shared preview resources. Offline styles can be displayed after these resources have been cached successfully.

**Are system background downloads supported?**

No. Regional map downloads currently use a normal `URLSession`, not a background session. Do not assume that downloads continue while the application is suspended.