the ivreg2h doesn't work--warning:variables have been centered

Hi All,

I tried to run the ivreg2h command in Stata to obtain the Lewbel IVs but failed. Following Lewbel(2012) I ran a version of the code below to estimate an instrumental variables regression model using Stata 17

ivreg2h ncskew_cmdos SIZE MB LEV ROA RET SIGMA DTURN FIRMAGE ABACC1 (dummy=),small robust fe gen(iv) z()

where ncskew_cmdos is yvar, SIZE-ABACC1 are xvars and dummy is endogvar. I planed to get the instruments through "gen(iv)"
But the code failed to work. The error is: "Warning: variables have been centered"
Array Array

What make me confused is that all the vars used for regression were not centered until I run the code(I use "codebook" to check the vars and surprisely find them have been changed after that). It seems that the "ivreg2h" code changes the vars and fails to work?

By the way, I used "help ivreg2h" and ran the example code in sequence, but the same error "vars have been centered" appeared again. Now I am wondering why the warning appears and how to solve it. Otherwise I am unable to proceed with the next step of work.(ivreghdfe--last estimates not found)

Any help would be much appreciated.

Landon Smith