Mac OS Sierra 10.12.6 does not detect startup USB for Mojave I would like to perform a clean install of Mojave as outlined in this article

https://setapp.com/how-to/clean-install-macos-mojave

However, my Mac Air 2013 does not detect my USB installer as a startup disk. I have tried twice to reformat the USB as macOS Extended Journaled and created a startup disk as outlined here, but still no luck (see screen shots below.)

Most suggestions online suggest reformatting the USB (which I have already done), but it still does not pick up the USB. I have also tried rebooting in recovery mode without the usb being detected.
To boot from the USB Installer:


Power-up your Macbook
Hold down the Option key immediately after the chime sound
Choose Install macOS Mojave from the list of entries
Install macOS Mojave