F::Q on Windows 8.1 works ok, Windows 10.0 no joy

[samsurd2]

For background, I've been using GnuCash 2.6.16 on an HP desktop running 
Win 8.1 and an HP laptop running Win 10.0 Home version.
I usually update quotes on the Win 8.1 machine, store the .gnucash 
account file on Dropbox and then download/run that file to the Win 10.0 
machine.
I do the reverse when I return from being out of town.
The same .gnucash account file and Finance-Quote 1.38 ran fine on both 
machines until Yahoo did its thing on Nov. 1.

Yesterday I did the following on the Win 8.1 machine.

1) Got a free AlphaVantage API key
2) Set a new Environmental Variable for both User and System 
(ALPHAVANTAGE_API_KEY=xxxxxxxx)
3) Removed the previously installed version of Perl from the machine 
(including running a registry cleaner)
4) Installed Strawberry Perl  5.26.1.1 (downloaded 
strawberry-perl-5.26.1.1-64bit.msi from http://strawberryperl.com/)
5) Ran "Install Online Price Retrieval" from the Start Menu which 
successfully installed Finance-Quote 1.45
6) Opened GnuCash and used the Security Editor Tool to change the quote 
source to Unknown -> alphavantage on all stocks and funds
7) Used Price Editor Tool to successfully retrieve new quotes (long 
list, took 2+ minutes)

Today, I did the following on the Win 10.0 machine.

1) Used the previously acquired AlphaVantage API key to set a new 
Environmental Variable for both User and System 
(ALPHAVANTAGE_API_KEY=xxxxxxxx)
2) Removed the previously installed version of Perl from the machine 
(including running a registry cleaner)
3) Installed Strawberry Perl  5.26.1.1 (downloaded 
strawberry-perl-5.26.1.1-64bit.msi from http://strawberryperl.com/)
4) Ran "Install Online Price Retrieval" from the Start Menu which 
successfully installed Finance-Quote 1.45
5) Opened the .gnucash account file from the Win 8.1 machine that was 
saved on Dropbox yesterday
6) Used the Security Editor Tool to verify that the quote source was 
already set to Unknown -> alphavantage on all stocks and funds
7) Used Price Editor Tool to attempt to retrieve new quotes
8) Got the message ("An error occurred while trying to...") produced 
previously when trying to get quotes from Yahoo.
9) Got a new AlphaVantage API key and used it to change the 
Environmental Variables
10) Used Price Editor Tool to attempt to retrieve new quotes and got the 
same unsuccessful result

Any suggestions for a next step would be appreciated.