I see that you have opened a MS Case for this issue which I believe is the right thing to do in this scenario. I do see that the publisher is Adobe Inc. (https://docs.microsoft.com/en-us/connectors/adobesign/), so we may have to get them involved. I'd say let's continue to move forward with the case.
Adobe Sign native Flow connector cannot not successfully run the “Get Form Field Data” action when the original sender is a different person from the Flow account holder trying to run the action. From what I could gather from support, this is by design for some unfathomable reason. This means that the connector is only useful for personal flows, destroying any hope of natively processing AdobeSign agreements in an enterprise setting. Adobe needs to fix this!
Encodian offers a Microsoft Flow connector that can successfully accomplish the “Get Form Field Data from PDF” action regardless of who the sender is. However, the Encodian solution is at a premium.