There are two methods within Moneydance for obtaining security prices and exchange rates automatically.
The extension “Quote and Exchange Rate Updater” found under EXTENSIONS – MANAGE EXTENSIONS. Check you are running the latest build v1024. For exchange rates use the source European Central Bank. Alpha Vantage covers the US as well as some securities outside the US, but is very, very slow. It’s my understanding that the source IEX Trading no longer works.
If the Quote and exchange rate updater does not work well for you try the extension Quote Loader under EXTENSIONS – MANAGE EXTENSION