Today during testing i found that i have forgotten to remove the updateKey in install.rdf and the addon points already to the new updates.json on a new https server. So i can not provide a corrected version, because the update.rdf is removed from install.rdf and the updates.json will not work with this key.
Finally i get this now:
Update keys are not supported for JSON update manifests
Of course the updates.json contains not the updateKey property its located in the install.rdf.
Looks like any further online updates are herewith stopped out and i have to distribute manually now. Any further solutions?