jupyter notebook running issues

I am running some python code using a jupyter notebook. The notebook should take a couple of days to finish. After a couple of running hours a massage is shown: “Error rendering Jupyter widget: missing widget manager.” The hourglass at the chrome tab keeps on running, but the * symbol next to the cell no longer appears, only [] is appeared. I have two questions: 1. is the notebook still running? 2. How can I fix this?