at some point they started blocking external connections from my wordpress-installation (probably global external-site-PHP-disallow!?). but after my support-request they re-enabled the specific wordpress-ip (the one from the error-message). so that the WP-installation can reach the external site again.
after that plugin-infos, download/update etc worked fine …
hope that helps!
resolved…of course it was a problem with my webserver. they simply don’t allow that kind of connections. but they at least had the wordpress-ip opened. so all is good now 🙂
