Kindly add the customary "RESOLVED" to the title of your thread for the benefit of all readers.mac_in_tosh ? TomH TX :
Thank you both for your input. Was finally able to successfully install the update! Followed a tip received from MacInWin (Jake) at MacForums. Booted while holding down the option key and choosing Internal drive from the options list.
This update is again showing up as available in the App Store. I thought I just did it ???