If you are exporting the data through the Developer Tool please verify the Developer Tool Log and the CMS log for additional details regarding the error.
A few common reasons for not being able to export the reference data are as below:
- User does not have sufficient permissions to CMS > Properties > Temporary File Location.
- Audit tables are not created at the corresponding CMS(Content Management Service).
9.6.x versions are way old. I hope you consider an upgrade.
For the failed task error message, you shall have a "Details >> " or "See Details >> " kind of button in the Failure Dialog Box --> Click on that & see if it gives any more information regarding the cause of failure. Does it?