ZoomRoom Exchange 2016 Calendar Integration error on iPad controller

[w0vos]

I have followed the online guides to setup a dedicated email account and attach the conference rooms to that account (the dedicated account is a delegate for all the rooms).  I have added the calendar integration via the zoom portal using the dedicated account, I have added the three conference rooms I have calendars for and I have assigned those calendars to their respective Zoom rooms.

In the portal, the status shows green and sync'd but on the iPad controllers it shows the error "The calendar credentials are either expired or invalid".  On a couple of threads on the support site said to re-authenticate and resend (which I have).   The portal continues to show sync'd and a green status but the iPads are still showing the same error. 

Any words of wisdom on a solution or how to debug the problem?