To run your code safely, the CodeRunner plugins submits the task to a sandbox server called Jobe using an HTTP request. That message tells you that the request failed.
There are quite a lot of possibilities but if this is a newly installed CodeRunner using the default Jobe server, jobe2.cosc.canterbury.ac.nz, the most likely explanation is that the Moodle server is preventing HTTP requests to that server. A firewall configuration, perhaps? You probably need to talk to a sysadmin, who should be asked to check the installation procedure for coderunner (https://github.com/trampgeek/moodle-qtype_coderunner#installation).
Please note that this default server is only for initial testing. The CodeRunner installation documentation explains how to set up your own Jobe server for production use. Further documentation is at https://github.com/trampgeek/jobe#jobe
There are quite a lot of possibilities but if this is a newly installed CodeRunner using the default Jobe server, jobe2.cosc.canterbury.ac.nz, the most likely explanation is that the Moodle server is preventing HTTP requests to that server. A firewall configuration, perhaps? You probably need to talk to a sysadmin, who should be asked to check the installation procedure for coderunner (https://github.com/trampgeek/moodle-qtype_coderunner#installation).
Please note that this default server is only for initial testing. The CodeRunner installation documentation explains how to set up your own Jobe server for production use. Further documentation is at https://github.com/trampgeek/jobe#jobe