ConvergenceWarning: Optimization failed to converge. Check mle_retvals. ConvergenceWarning)

This warning message is typically encountered when running maximum likelihood estimation (MLE) models in statistics. It indicates that the optimization algorithm used to estimate the parameters of the model did not converge to a solution within the specified maximum number of iterations.

In other words, the algorithm failed to find the optimal set of parameters that would maximize the likelihood of the observed data given the model. This can occur for a variety of reasons, such as poorly specified model assumptions, non-linear relationships between variables, or insufficient data.

To address this warning, you may need to adjust the model specification or try different optimization algorithms to see if they can converge to a solution. It is also important to check the mle_retvals output, which contains additional information about the optimization process and may provide insights into the reasons for the convergence failure.