Hi all, this is my first post.

I am currently attempting to fit a two factor hierachical model with a random subject effect (for nested design). However, when I run my model I get the following message "The final hessian matrix is not positive definite though all convergence criteria are satisfied". When I look at my estimates of covariance parameters table, I find that my Intercept (subject) variance is zero, with the message that my covariance parameter is redundant. If anyone can explain what is occuring and give me some advice on how to fix it, I would be very grateful.

Thanks.