There is a current known issue with the 4.0 release of the SRA with ActiveDR when the replication link is paused between the source and target pod.
The Synchronize Storage step will appear to hang at 100%:
Go to the either FlashArray in the ActiveDR pod pair, and navigate to the pod and in the Pod Replica Links box click the vertical ellipsis and choose Resume:
Confirm the resume operation:
The test recovery will then complete once synchronized. If you prefer to not re-enable replication but still perform a test, cancel the test recovery and de-select the Replicate recent changes to recovery site option.
This will cause the synchronization to be skipped.