[GNC] Unable to retrieve currency quotes

[ml enquirer]

Hi,

I have GnuCash 2.6.21 for Mac (running 10.13.4). I have set up
Finance::Quote properly, with my alphavantage key. When I press "Get
quotes" in the Price Editor, I expect updates for CHF, EUR and several
stock quotes. The stock quotes come back fine each time, but the two
currency updates fail every time:

Unable to retrieve quotes for these items:
  CURRENCY:CHF
  CURRENCY:EUR
Continue using only the good quotes?

Why are the currency updates failing, when the stock quotes succeed? How
can I debug? (I already tried looking at the gnucash.trace file, but
there's nothing obvious appearing there. ./gnc-fq-dump works fine...

Please help! :(

D