facebook link cannot be saved

Hello,

when I try to modify the settings of the plugin and try to enter the url for facebook and click on “?NDERUNGEN SPEICHERN” I get an error message saying:

There was a problem with your action. Please try to reload the page.

I reload the page, my settings still are there but the same when I hit the button.
The error message is coming up all time.
When I change the url to the facebook page like without the “https://” it can be saved, but then of course the link is wrong and will be just added to the end of the url of the website like https://www.homepage.de/facebook/whatihaveentered
Wordpress 5.6.1 / Fuse Social Floating Sidebar 5.3.2
Thank you for any help.

BR
Thomas

The page I need help with: [log in to see the link]