W' Metric is not working

Hi, I have a problem visualizing W’bal. The metric seems either to have a value of 0 or no value at all. The graph is never displayed even when I activate it. I tried both creating my custom graph or using one created by someone else but none of them work. The same problem happens on all my activities, garmin or zwift recorded.
Thanks for the great work you do !
Fabien

Have you set a W’ J value in the settings screen?

I added “W’bal” to a recent ride of yours and it seems to be working?

Yes thank you , it works now. I added a J value in the setting screen!
Many thanks!
FAbien