are you sure you are running the right blender from the command line? from you description it seems like the animation nodes plugin is not being loaded, that’s what happened when I tried to render an AN animation without the plugin being loaded.
Probably that’s not the case, but just better to make sure
Aside from this not sure what it could be.
EDIT: another thing to make sure is if you have the update on frame change option active in the animation node editor