I am trying to use Mplus to run a moderated nonlinear factor analysis (MNLFA), as described in Bauer and Hussong (2009), for which I have included sample code below. In this model, the measurement parameters relating an indicator (y1 below) to a latent factor (eta below) are affected by a covariate (x below). Additionally, the variance of the latent variable is affected by this covariate.
In the past, I have been able to run this exact model with continuous, ordinal, and binary outcomes. However, in this particular case, y1 is a count variable, and the model will not estimate. (In particular, I get an error message which says, "FATAL ERROR: THIS MODEL IS NOT AVAILABLE.") I've tried a bunch of workarounds, such as using the XWITH parameterization, but have had no luck.
Do you have any ideas or suggestions for how I might be able to fit this model using Mplus software?