OK,
See my answer on your other post. Looks like your error come from bad parametrisation of "extremities" or corresponding hydraulic laws.
For steady run using "steadyValue" attribute of "extremities" layer, "type" of "extremities" must be "limnigraph".
If you want to use it with rating curve, "type" of "extremities" must be "Taring curve Z=f(Q)" and the hydraulic curve must be set up in hydraulic laws menu (activate it, give the correspondig extremity, Taring curve Z=f(Q) and edit it).
Alexis