OWA Attachments appear as '65B'

I've recently built a new Client Access Server in our Exchange environment and to allow clients to get archived attachments when using external OWA, I installed the EV OWA extensions, added the new servers name to the 'ExchangeServers.txt' file on the Enterprise Vault server, ran the OWAUser.wsf script to apply the EVAnon permissions and restarted the EV services. Since doing this though, I am unable to retrieve any archived attachments no matter what CAS I connect to and they all appear as '65B'. I enabled EV logging and connected to OWA but I can see '[EVContext::LoadHiddenSettings] Retrieved hidden message from web services' so everything seems to be ok. Do I need to re-install the EV OWA extensions after running the OWAUser.wsf script or does anyone have any idea why this isn't working?