In some cases, due to improper login to at the onset, user may have issues with opening attachments in OWA
a faster way to resolve this is by using adsiedit
Resolution:
while in ADSI, go to properties of user and set this attribute MSExchMailboxFolderSet to 2147483647
This setting enables all OWA features.
Note: In some cases, user still has his/her outlook web access frozen and not able to do anything.
re-creating user’s profile on the workstation fixed the problem
Ex-Shell 