Mike
If you are downloading ok it must mean that there is more than one instance of the software on the computer and it is going to the other instance.
Did you load to program files or the recommended c:\Airnav or the like
Use Windows search to find NavData.db3 and drag it into your data folder. Ignore any other similar file with different extensions. There will be one in there already, the original one that comes with the software but if you downloaded an update the updated file must be on your computer somewhere. Find the update you downloaded and drag it into the data folder replacing the one already there.
Alan