SSIS Oracle Connector - AcquireConnection method call to the connect manager failed with erro code 0x80004005

I'm trying to connect to an oracle instance with the attunity connector and getting this message when executing package from Visual Studio and when deployed on the server. Connection succeeds when tested in connection manager and allows me to preview data within the designer.

I have in place so far:

• Both 32 bit and 64 bit attunity clients installed
• Oracle authentication with encryption mode set to encrypt with user key (in case the password wasn't been consumed correctly).
• Fully qualified TNS name with host/port number

Occasionally one of the packages will also show error 'Oracle home not found' or 'failed to load OCI.dll' but this isn't consistent and will only appear on one of the packages. Also not sure whether the oracle home parameterisable fields (which aren't exposed through the connection manager) need to be set - though tried setting this to the server-side oracle home location and this hasn't worked either.