If you are using Mac OS Catalina Beta Version released in June 2019, you might probably have difficulty in opening Anaconda, which appeared as above under beta system.
Following is a way that I used to solve this issue (if you installed the Mac OS beta version on all of your PCs like me and still need to learn/use):
In Terminal, install Jupyter with pip; then open Jupyter notebook through Terminal/ working under vscode with respect interpreter
pip3 install jupyter
It will promote to Jupyter Notebook in your web browser.
VS code can also be used after select repected interpreter and you can begin using #%% comment as following:
References are available here.