[Plugin: wp-comment-master] How to edit line: There was an error submitting the form..

Hi,

If I don’t fill in all required fields I get a system message in red:
. There was an error submitting the form. Check below to see what happened.

Does anybody know where I can edit this line?
I could not found it in the theme I use (shell-lite), not in this plugin and not in WordPress language.

Guido

https://www.ads-software.com/extend/plugins/wp-comment-master/