Looking from the img alone I can see that you are currently looking at an animation file (.can3) not the model (.cmo3), and that is why you can export the motion file, go to the model file and try again.
Also there are some limitations for the free/trial version (take a look here, so if you can't export while looking at the model, you probably have passed one of them.
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Also there are some limitations for the free/trial version (take a look here, so if you can't export while looking at the model, you probably have passed one of them.