Invalid Value on backend Plugins

[HoffErik-JohnerInst]

I tried using this Plugin (free tier v1.4.3) on my Typo3 Page (V10.4.31) following this guide: https://www.miniorange.com/typo3-single-sign-on-sso

After activation, I created pages FESAML, RESPONSE and Logout and tried to place the plugin blocks on the corresponding pages. On save, the selected plugin value switched to invalid value('fesaml') (or response)

In FE the page was empty.

The Login Module wasn't even listed in the plugins tab of the block selection window.

Any help appreciated.