Hello everyone

I am trying to estimate a linear model with an endogenous covariate by following the procedure: statsistics / endogenous covariate / models adding selection and treatment / linear regression on STATA15. See : https://www.youtube.com/watch?v=bPhNq6RYd-I

My dependent variable of the main equation is continuous, and my endogenous covariate is ordered.

When I run the procedure, I have an error message r (430): Could not calculate initial values; tray specifying from ( ).

When, I estimate the main equation without correction of the endogeneity to obtain the initial coefficients to integrate in the option "from ( )", I have another error message r (503): initial vector: matrix must be dimension 28. I can not find any references to that.

Please, I need help to solve this problem. If anyone knows how to make this procedure, I will be very grateful.

Best Regards.
Fateh.