Zero-Inflation NB - object 'model_count' not found - r

Question

I am modeling a mediated zero-inflated negative binomial (ZINB) model. i am following the steps of O'Rourke & Vazquez (2019) --> https://www.sciencedirect.com/science/article/abs/pii/S0306460319301078
A few days ago i was running a different ZINB model which ran perfectly fine. However, today i wrote a different model, same variables, but somehow it doesn't run anymore and gives a strange error. When i try my previous model i suddenly get the same error, namely:
Error in zeroinfl(Y1 ~ X1 + M1 | X1 + : object 'model_count' not found
The rest of my code:
#loading required packages
library(psych)
library(foreign)
library(ggplot2)
library(MASS)
library(pscl)
library(nonnest2)
library(lmtest)
library(boot)
#Import data
mydata
#Fit a ZINB model
ex1zinb <- zeroinfl(X1 ~ Y1 + M1 | Y1 + M1, data = mydata, dist="negbin", EM= TRUE)
I already checked the assumption for the statistical analyses etc., and it is especially strange that a similar model did run a few days ago and not anymore. I did try to install several packages today but i ran into a non-zero exit status. Following some comments on stackoverflow i installed a package by adding dependencies = TRUE, but it ran stuck. Afterwards the problems started. Maybe there is something wrong with my packages?
When loading the libraries i get the following messages:
> library(psych)
> library(foreign)
> library(ggplot2)
Need help? Try Stackoverflow: https://stackoverflow.com/tags/ggplot2
Attaching package: ‘ggplot2’
The following objects are masked from ‘package:psych’:
%+%, alpha
> library(MASS)
> library(pscl)
Classes and Methods for R developed in the
Political Science Computational Laboratory
Department of Political Science
Stanford University
Simon Jackman
hurdle and zeroinfl functions by Achim Zeileis
> library(nonnest2)
This is nonnest2 0.5-3.
nonnest2 has not been tested with all combinations of model classes.
> library(lmtest)
Loading required package: zoo
Attaching package: ‘zoo’
The following objects are masked from ‘package:base’:
as.Date, as.Date.numeric
> library(boot)
Attaching package: ‘boot’
The following object is masked from ‘package:psych’:
logit
Anyone some suggestions/insights?
Thanks in advance!
Edit: i do get a normal output when running a non-zero inflated negative binomial model. The following code runs smooth:
summary(ex1nb <- glm.nb(Y1~ X1 + M1, data = mydata))
So i think my data is fine?

Answer 1

I got that error too. I used R 4.0 then tried R 3.6. No luck.
I was able to get the error to go away when I removed the EM = TRUE parameter.
I'm not sure if this helps.

Answer 2

Author of the paper here (O'Rourke) - this was due to a pscl package update where they changed the location of the EM statement. We have updated the code for the paper removing the "EM=TRUE" statements from each relevant section and are in the process of getting it on github so we can flexibly update in accordance with any other package changes. Please feel free to reach out if you have other issues with the code.