If the client starts with https, the browser does not allow communication through http. This is configured in the system.properties file.
Modify the url in the system.properties:
# URL to the CardSDK. Used for card preview/production, image capture
# for https (note: it's a different port):
# for http:
Make sure the browser accepts the root certificate of the CardSDK certificate. You can upload it to the browser's certificate store for trusted CAs.