My guess is that the problem is that you’ve run the training for a lot of iterations and that has caused the memory footprint of the notebook to become too large and that is why the browser tab is throwing the error. What you need to do is click “Kernel → Restart and Clear Output” to discard all the generated memory, but if you can’t get control of the UI before it throws the error, it will be pretty hard to do that. Do you see the notebook menu at all as it is coming up? You can try clicking and see if that works or not. If that fails, then we may need to get the course staff to step in here. The mentors do not have the “superpower” to look at let alone modify anyone else’s notebooks.
There is a topic here about how to get a clean copy of a notebook, but that also requires that you be able to get control of the UI in order to execute these commands.
Please give the “Kernel Restart” thing a try and let us know if that doesn’t work. Then we can appeal to a Higher Power!