Error when installing from unpacked files

[mdicss]

Hi
I just downloaded the extension and tried to install it from the local filesystem. I get the following errors

Failed to load extension
File
X:\software\dynatrace\extensions\DynatraceDashboardPowerups-master
Error
Could not load background script 'bg_secure.js'.
Could not load manifest.

Any idea how to correct this? Installing directly from chrome store works. I used Chrome 94.0.4604.71 and 97.0.4692.71.

Regards
Matthias