You're missing a few key pieces of information... Are you using the ordinal package ? What code did you use to call anova ?

This comes from the depth of R. It means that the command anova() expects a different object type. Usually, it would simply be two model objects, like:

anova(modelnull, model1)

The object you pass to anova() is a vector of numbers. Looks like you have passed a vector of coefficients to anova, not a model object.

Hi Sal Mangiafico and Martin Schmettow

I used anova(modelnull, model1) and yes I am using the ordinal package.

It's difficult to diagnose from here. Do you get a meaningful result for summary(model1) ? Do you get a meaningful result for anova(model1) ?