UserWarning: The number of elements in the out tensor of shape [1] is 1

I am using HuggingFace pytorch-transformers and one of my pre-trained models refuse to fine tune giving me those UserWarnings for every call.

I have described the details in

But someone downgraded my question for some reason. What am I missing?

Here is my Notebook so you can run and see the results:

Thanks for your help!