The problem was a redundant free/busy folder left over from the old Exchange 2003 Server. You could see that by running
get-publicfolder -identity \NON_IPM_SUBTREE –Recurse – it mentions First Administrative Group as a Free/Busy folder.
It had no replicas so we added one using
C:\>set-publicfolder -identity \NON_IPM_SUBTREE\SCHEDULE+ FREE BUSY\EX:/o=2007/ou=First Administrative Group -replicas "public folder database"
O and OU are variables that can change per Exchange install.