Starting the archiver via HTTPS fails with self signed certificate

Dear Developers,

I already posted this on the Piwik Forum but was asked to post it on GitHub as well.

Due to a shared server I have to run Auto-Archiving via Webcron. I followed the instructions provided by Piwik to implement the Auto-Archiving via Webcron. But when I paste the URL (https://subdomain.domain.com/misc/cron/archive.php?token_auth=correct-token) into my browser, I get the following message:

Error: Die Methode 'runCronArchiving' existiert nicht oder ist im Modul '\Piwik\Plugins\CoreAdminHome\API' nicht verfügbar.

Which translates to: Error: The method 'runCronArchiving' does not exist or is not available in the module '\Piwik\Plugins\CoreAdminHome\API'.

Does anybody have a clue what I may be doing wrong?

I do have an old install of Piwik with Auto-Archiving enabled (also with Webcron) and this installation runs without any problem.

Thanks in advance for your help! It is very appreciated.