Great, thanks Kelly.
When you have a moment, could you please try the following with your notebook and then attempt to run Density-based Clustering with the OPTICS method again to see if the problem is resolved?
1. Open your notebook item page, where you saw the notebook runtime dropdown.
2. Ensure the notebook is not open on any browser tabs.
3. Change the runtime to ArcGIS Notebook Python 3 Advanced - 7.0
4. Open the notebook and attempt to run Density-based Clustering with OPTICS.
Please let me know if you have a moment to run this and if the tool runs as expected in that new runtime.
Thank you for your time,
Alberto