"Discontinuous region encountered" error on xtoprobit command

Hi all,

I am running into an error when trying to use the command xtoprobit, it comes back saying "cannot compute an improvement--discontinuous region encountered." My dependent variable is made up of integer values from 0 to 3. I have tried to rescale and create new variables by multiplying the variable by 3 and dividing it by 3. The error is still there when I use the xtoprobit command.

Does anyone have any suggestions?

Thank you very much!