SSD install failed after update

Was running Home-Assistant on RPi 3b+ with an external SSD drive (120GB Sandisk conected to USB). Everything worked flawlessly until I updated Home-assistant few days ago.
Since the update the I can no longer make the RPi boot from the SSD with a fresh install. I can boot from a USB disk on key connected to the RPi which confirms that I can boot from the USB. What am I missing?