Better GRBL support missing setting

I have recently started with a fresh version of octoprint installed on a RBi 3b+, I have installed the better grbl support, in the plugin's tab near the bottom it is missing the GRBL settings, saying signature : unknown.
does anyone have any suggestions?

as a side not I had it all working a couple days ago, but messed something up and had to do a fresh install of octopi, using the same settings but still not working.

thanks for the help

Looks like that the that there is already an error report in the plugin developers repository: