The kernel for Jupyter Notebook does not start

1. I have just installed **Anaconda 3** (Python 3.7 version) on a macOS Mojave system. Installation went smoothly and includes the latest version (5.1.1) of **ipykernel**.
2. As I launch **Jupyter Notebook 5.7.8**, Safari opens correctly and shows the usual folders' navigator.
3. Nevertheless, when I launch a Jupyter Notebook, the kernel *does not even start* and all I get in the terminal window is:

> [W 16:56:44.626 NotebookApp] KernelRestarter: restart failed
> [W 16:56:44.627 NotebookApp] Kernel b656dc1a-b221-4d35-b473-dfbcf1d593a3
died, removing from map.
> [W 16:57:29.624 NotebookApp] Timeout waiting for kernel_info reply from b656dc1a-b221-4d35-b473-dfbcf1d593a3
>[E 16:57:29.627 NotebookApp] Error opening stream: HTTP 404: Not Found (Kernel does not exist: b656dc1a-b221-4d35-b473-dfbcf1d593a3)