If you are encountering issue that downloaded offline maps are not shown on main map screen in GPX Viewer PRO this may have several reasons. Solutions which will solve most of the cases of this issue are as follows:

1. Try zooming out by - button in bottom right corner as much as possible.
2. If no map will be shown. In top toolbar tap on map button without globe. If you hidden this button previously tap on … button in top right corner in this top toolbar and from menu select Offline map. If you have also hidden this button, open left main menu, then tap on Settings button. In settings screen tap on Maps button and then Offline maps manager, when you do this you can continue to step 4 of this how to.
3. In Offline map dialog click on Download button at bottom.
4. In Offline maps manager tap on + button in bottom right corner and tap on Worldwide low zooms map data. When download is successfull go back into map screen. If no map is shown, continue to step 5 of this how to.
5. Uninstall GPX Viewer PRO from your device.
6. Restart your device.
7. Install GPX Viewer PRO from Google Play Store again.
8. Try downloading worldwide offline map and see if it is working.
9. If worldwide offline map is working, try downloading other offline maps.

If this doesn't solve your problem, please create ticket at our support system https://support.vecturagames.com/gpxviewer.