How to find out which securities need to be switched from Yahoo to Alphavantage

[David Carlson]

I have been using GnuCash for many years and there are many securities in
my file that I no longer own, but I may or may not have discontinued
downloading their prices.  In trying to get my Alphavantage source working,
it appears that it does not work if there is a mix of some securities
changed and many not changed.

1. Do I have to find all of them and change all before it will work?

2. If so, is there an easy way to find them all?

3. If not,what troubleshooting steps will help figure out why it is not
working yet?

David C