Report Distributor is not accessible in the Preview site for a Workforce Analytics instance (e.g. analytics4.successfactors.com/Preview).
SAP SuccessFactors Workforce Analytics
The ability to access Report Distributor from the WFA Preview site was deliberately and universally restricted back in 2012, as it did not serve the intended purpose of Preview as opposed to Production (i.e. onsite data validation prior to publication to Production). The internal reference for the work done is WFA-632.
Use Report Distributor on the Production site, or view reports on the Preview site itself rather than by distribution.
KBA , LOD-SF-ANA-RDT , Report Distributor , Problem