Zenec E 3756 - under voltage protection sensory circuitry

[Elvis the fish]

My van has been sitting for three weeks without starting - solar panel has maintained power to the vehicle and habitation batteries and the engine caught first time this afternoon if a little sluggish.
My Zenec 3756 didn’t come on as usual with the ignition nor did it power up during the drive - my first thought is a blown fuse which I have yet to check but I have read up about the under voltage protection sensory circuitry used to protect the unit during starts where the starting power may be low or not consistent - anyone any experience of this situation please?

 

[mitzimad]

zenec?

 

[tonka]

zenec?

Fitted in some fiats. I have one in my 2014 Burstner. Not the best but was ready fitted.

Not aware of the under voltage issue.