[Limdep Nlogit List] Ordered probit with sample selection

[Tartari, Valentina]

Dear all,

I am trying to estimate an ordered probit model with sample selection. The first step (probit) works fine, however when I try to run the second step I get this message: "Error 128: Models - Insufficient variation in dependent variable".

My dependent variable is coded 0,1,2,3 and if I run an ordered probit without the selection it works fine.

Any idea of what can be the problem?

Thank you a lot

Valentina