2015 Kalkhoff Tasman problems (Impulse 2.0 motor) problems

[Kennygee]

My wife bought the above cycle last year with only 500 miles on it, very good condition Apart from very briefly losing drive a couple of times which we just consider to be minor glitches everything else has been fine. However last week after a full battery charge there is no longer any assisted drive. Battery is fully charged, 41 volts, and the handle bar switch and display (small type) appear to be working correctly and showing speed OK. I have removed the side cover and the terminations seem OK. I don’t think it’s a mechanical issue as the push assist still works fine and there has never been any untoward noises, slipping etc, it’s almost as if it’s not picking up pedal movement to kick in. I’m tempted to open up and investigate as I have elec/mech maintenance background and there’s no dealer around here (Norfolk). Has anyone out there had a similar experience, it would be nice to have a couple of pointers or info before I start diving in.