Extreme power with Real Turbo Muin (without B+ sensor)

Hi,

I have been a Zwift user for almost a year.  I use an Elite Real Turbo Muin B+ (s 13867) trainer but strangely, there is no B+ sensor in mine! 

Never was a problem.  Right out of the box, the trainer worked perfectly when I pair it as a power meter.

Suddenly this week, I logged on Zwift and then I get 400 watts by barely spinning the pedals!  I have read severals posts concerning high wattage with the Elite trainer but lots of them mention the B+ sensor which I don’t have.

If anyone could help, would be very nice.