Creating new calendar from URL fails

I try to create a new calender from this URL:

https://www.eifelverein-eupen.be/index.php?option=com_jevents&task=icals.export&format=ical&catids=0&years=0&k=38f31bbc7bff3bce9137ac0e5a56adc2

It fails with the messages:

Hinweis

file_get_contents() failed, try fsockopen

and

Fehler

Not a valid VCALENDAR data file: httpshttp://www.eifelverein-eupen.beindex.phpoptioncom_jeventstaskicals.exportformaticalcatids0years0k38f31bbc7bff3bce9137ac0e5a56adc2

Downloading the .ics file and creating the calendar from it works like a charm.

We are running:

PHP Version : 7.0.30

MySQL Version : 5.5.56-MariaDB

Server Information : Linux srv28755.managed-pleskserver.de 3.10.0-042stab127.2 #1 SMP Thu Jan 4 16:41:44 MSK 2018 x86_64

Fix jQuery? : Yes

Load JEvents Bootstrap CSS? : Yes

Max Input Vars ? : 2000

Club code set? : Yes  

User Agent : Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0  

Joomla : 3.8.11

component_com_jevents : 3.4.47

component_com_jce : 2.6.23

module_mod_jevents_cal : 3.4.47

module_mod_jevents_custom : 3.4.47

module_mod_jevents_filter : 3.4.47

module_mod_jevents_latest : 3.4.47

module_mod_jevents_legend : 3.4.47

module_mod_jevents_switchview : 3.4.47

plugin_content_jevents : 3.4.47

plugin_finder_jevents : 3.4.47

plugin_installer_jeventsinstaller : 3.4.47 (not enabled)

plugin_search_eventsearch : 3.4.47

plugin_system_gwejson : 3.4.44