Changed to SSL and can not send anymore

Hi there,
I use the latest version of Joomla an JoomlaMailer. Since I switched from http to https (SSL) and to PHP 7.x, I can not send Campains anymore. I have to remove my .htaccess-Protection to Preview a Newsletter. Also I have to remove the .htaccess-Protection to SEND the Newsletter. If I put them in I get an error:

"Fehler
Ungültiger Inhalt! (Der Server antwortete mit einem Fehlercode. Möglicherweise existiert ein Passwortschutz, der den Zugriff verhindert.) (Fehler: The HTTP server returned error code "401". Only a 2xx response is acceptable: https://www. mydomain . de/administrator/components/com_joomailermailchimpintegration/archive/mynewslettertitle.html)"

So please, could you have a look at this!
Thanks
JamFX