Notebook stopped working

That probably means you have added print statements that generate a lot of output and the memory footprint of your notebook has grown very large. What you need to do is launch it and then click “Kernel → Restart and Clear Output” to release the memory. But if you can’t start the notebook, that’s going to be a problem.

If you are still on the Regularization Assignment, there is a way to get back to a clean copy of the notebook. Fortunately all 3 of the C2W1 assignments are in the same Docker image. So launch one of the other ones (e.g. Initialization). Then click “File → Open” and then navigate up to the “release” folder above that assignment and then down into the one that is failing. Then do a “rename” to rename your notebook to a different name. Then try to launch the failing one again and you’ll get a 404 error. From there, follow the “get a clean copy” procedure from the FAQ Thread. That will get you a new fresh copy that you can then launch. Now the problem is how to copy over your completed work. If you can’t open the broken notebook, you could try downloading it from the file navigation menu (the renamed copy). Then if you can launch it locally, you might be able to “copy/paste” over the code. Or you could try uploading it to Colab and copy/pasting from there.