Icons in moodle plugin questions types don't show in all browsers
I have an issue in the moodle plugin question types. In IE, Chrome and Firefox icons are not shown in the h5p moodle plugin, version 1.7. Moodle is version 3.4. Screenshots are attached. I actually tested with Moodle version 3.1 also and also h5p plugin version 1.5 and 1.6.
Any help or advice what might be the issue would be appreciated.