I am trying to estimate a probit model with xtpdyn.
However, when I run

Code:
xtpdyn hnpl gdp lir capad roa, uh(gdp)
xtpdyn, keep
 margins, dydx(capad gdp) expression(normal(predict(xb))) force
I get an error

Code:
. xtpdyn, keep
one or more variables already defined
I uave written that this may be caused by the presence of "_" in the name of the variable but this is not my case. If I replicate the command on dataset implemented in Stata by webuse, I don't get any error.