Cannot access Subsite after update to 4.3.1

Just updated our Multisite install to the most current version 4.3.1, this install was a few versions old. Everything went pretty well except, 1 site out of the 20+ subsites we work on cannot be accessed(live url or dashboard).

We think the issue is the Twenty Ten theme and the fact it is out dated. I have tried going to Network admin -> Sites -> brokensite -> Edit -> Themes and change the available theme that way. It has not worked when we have changed themes there.

Any suggestions on a different path to take and get the site up again?