I had a similar problem yesterday on a site I upgraded from 2.5.2 to 2.6.
I had access to the resource tree but the Security Feed and MODX News feed were showing up just like yours.
In my case I had also migrated the site to SSL (https).
In the Manager folder I found that the .htaccess file had
enabled. This allowed me to access the manager via http, although I didn't notice I was doing that.
When I commented out the
instruction the manager loaded via https and the two feeds came back.
[ed. note: andytough last edited this post 2 years ago.]