Rally XC200 pedals and L/R power data

Hi, I have rented some XC200 power meter pedals. I tried a quick ride with them connected to my Forerunner 255 watch, and afterwards I can only see basic power data, with no L/R balance.

I have put fresh batteries in, calibrated, and as far as I can tell from the connect app the pedals are linked. 

Can anyone help please?