Auto testing can be done only for Flows in the Draft, Ready, or Production stages, and not for Flows in the Archived section.
Case 1: You archived a Flow, but there is still a version in Draft, Ready, or Production.
You can still auto test the Flow.
Case 2: Your archived Flow is the only version on the Dashboard.
You cannot auto test the archived Flow. Any existing test cases for the archived Flow are removed.
Info
When an archived Flow is restored, its test cases before archival are also restored. You can also create new test cases for the restored Flow if required.