Michael Newton if this does not work there is also a force update you can do by doing this.

go to periodic folder >> then rename .htaccess to somthing like .htaccess.bak >> then go to your site in studio go to settings >> check the box force auto update even if some files where modified >> then go to this website https://www.yoursite.com/periodic/cron.php

i upgraded 4-5 times in a row this way to version B1 >> Rc1 >> Rc2 >> 10.0.0

the way to know it worked is if you get a white page after the white page stops loading your all good just refresh the dashboard within admin studio to see the new version now updated

also dont forget to rename .htaccess.bak back to .htaccess