Found a good article on the Nutt Hydraulic brakes that was very helpful.   First one is to top off the the second is to do an actual bleed.

Top Off

https://www.youtube.com/watch?v=5wpsz1nwaBc

Nutt Brake Bleed

https://www.youtube.com/watch?v=pW_jwFDmFxk

Sad, all I get is an add from the Forum.  After some research, the Brakes are made by Nutt and use Mineral Oil.  Easy enough, just got a kit and some mineral oil followed  youtube video and I was good to go.

Hi All,

New to the forum.  Great discussions.  I have a 19 mile 2021 Rad Rover 6+ that the front brake needs work.  The lever goes all the way to the handle.  Previous owner said they accidently caught the lever and it pulled the plunger out of the reservoir.   The plunger is now replaced and the I am left we a unresponsive brake.  What type of fluid does it take to fill the reservoir to test it?