Thanks, itimpi, for your help; I resolved this problem by selecting 'replace the USB'. I was concerned about the original USB and had made a new one, but in my ignorance about how this works, I failed to go through the proper procedure for transferring to a new USB. I am a 'newbie', but hope to learn more about the unraid operation.
I started an Unraid trial in Dec 2025 and extended it in Jan 2026. I then proceeded to purchase a starter license. I used the email instructions to create a 'stater.key' which I copied to the /config folder of the USB key which I was using. Now, when I try to boot the array, I get this error message: Invalid, missing or expired registration key. Any help would be appreciated.