Avid Pro Audio Community - Avid Link: updates fail, no auto-login, no auto-install

Hi
I have Avid Link 19.5.0 Build 568 installed on a MacBook Pro Retina running MacOs High Sierra 10.13.6.
I tried everything from "clear cache" up to reinstalling Avid Link.
All "auto"-functions seem not to be available to me.

I have to manually login in to Avid Link every time I start my computer
Updates fail all the time, when I start them from main Avid Link page after having logged in manually: they download, extract, seem to install, ask computer admin credentials and then display as "failed"
The option "install in the background" also fails. It will ask for my computer's admin credentials, seem to install in the background, but also display as failed.

The only way to install updates is to go to MyAvid-account, download the updates and install them manually.
So: since Avid Link does not log in automatically, I will never be automatically informed about available updates nor will I be automatically be able to work with cloud storage for projects. With whatever version of Avid Link I had installed, I always had to manually log in, first. Also the software update-problem never went away with whatever version of Avid Link I had installed.

I suppose, this is not the intended way, Avid Link should work, right?

Any advice how to get this working, is very appreciated.