The main reasons of having problems when downloading symbols are:
- Incorrect configuration of launch.json file.
- No License/incorrect license was uploaded on the server.
- User does not have enough permissions. You can try running VSCODE as an administrator.
- Symbol generation and Developer service endpoint are not enabled in the Dynamics NAV Administration App.
- Service was not restarted after service tier modifications.
- NetFx40_LegacySecurityPolicy needs to be set to false.
We have answered more questions after our extension webinar here