Alright, then could you try to create a new conda environment and check if that’s working?
To work with environments, have a look at this doc 6.
Basically, you could try the following in your terminal:
conda create -n pytorch python=3.7 anaconda
conda install pytorch torchvision -c pytorch
conda activate pytorch
jupyter notebook

Note that you might want to change the Python version or the pytorch install command if you are using another version.
We already had some issues with notebooks not being able to find certain packages and the reason for this is usually a misconfigured environment.