If OMN macOS won't startup, the following should get you up and running again.
OMN keeps your data in '/Users/<Username>/Library/Containers/com.anquet.omnmacos/Data/Library/Application Support/Outdoor Map Navigator'
The ‘Library’ folder is usually a hidden folder. Here are the steps to open the folder.
1. Open Finder
2. Hold option key and click ‘Go’ menu. You should see a ‘Library’ menu item. If you don´t see it, use Go to Folder, and past in the following (without the quote marks): "~/Library/" and press Go.
3. You should now see the ‘Library’ folder contents.
4. Click into the Containers folder
5. Click into the com.anquet.omnmacos folder
6. Click into the Data folder
7. Click into the Library folder
8. Click into the Application Support Folder
9. Click into the Outdoor Map Navigator folder.
10. You should find two files which we want to delete: settings.xml and omn.db - please delete them both.
11. Restart OMN, and it will now ask you to login and sync with Anquet Cloud
OLD SOFTWARE VERSIONS
If you are running OMN with a version number less than 1.04, then your data is most likely in this folder:
OMN keeps your data in ‘/Users/<Username>/Library/Application Support/Outdoor Map’Navigator’.
If you aren't sure which, our recommendations are to move to the latest software so:
1. Using the instructions above, remove Settings.xml / omn.db from this directory: '/Users/<Username>/Library/Containers/com.anquet.omnmacos/Data/Library/Application Support/Outdoor Map Navigator'
2. Install the latest OMN macOS software from OMN macOS Releases
3. Run up OMN macOS - this will move any mapping from the old location to the new location if required.
4. Remove everything in this directory: /Users/<Username>/Library/Application Support/Outdoor Map’Navigator - this will clean your system of any leftover files from the old installation location.