Thomas Döring I'm using 2.0 and this is not an issue for me anymore. It actually wasnt the plugin's fault but a misconfiguration of the nginx proxy ssl certs.
I put an nginx proxy infront of Jenkins to handle the ssl stuff. When adding the cert you must concatenate the server certificate and the CA certificate together. For example:
cat servercert.crt ca_cert.crt > nginxcert.crt
If you dont do this and only use servercert.crt, everything will look fine if you use a browser to go to Jenkins but when you use a tool like curl, the cert will not be trusted. I've seen other system tools behave this way and have also seen this when using SSL libraries for some programming/scripting languages which is probably why GitHub's markdown renderer didnt want to load the badge. After configuring this properly, the badge loaded with no problems.