HTTP 403 error in anonymous mode #1431

What is this message that keeps appearing over my screen each time I expand an article to read?

"A request has failed, it may have been caused by Internet connection problems."

details of my system:

centos 7.3.1611
nginx 1.11.10
php 7.0.16 (w/ php-fpm)
mysql Ver 15.1 Distrib 5.5.52-MariaDB
server also has redis running

the freshrss logs are empty/non-existent.

most of the feeds i have subscribed to come from feedburner.

my site is served via ssl.

anything else i'm missing? Thanks.

Fabian S.