For those interested, I think I found the problem. While running a cron on the new site a large number of errors occurred with the
core\task\build_installed_themes_task
The error indicated :Fatal error: Maximum function nesting level of '256' reached, aborting!
Following some research, it appears to be related to the ZEND_EXTENSION: XDEBUG.
I commented it out of my php.ini and reran the cron. It happily completed the ad hoc task and surprisingly I was able to try the BOOST theme with no issue!
Hope this can help other users.
Eric