Hi @Anonymous,
Could you please share a full screenshot of your flow's configuration?
Could you please show more details about the error message (Which action holds this error)?
I agree with @JohnAageAnderse's thought almost, you could send an approval email to yourself for testing before sending it to other approvers. I think this issue is related to your flow's configuration.
If you add the "Start an approval" action within the "Apply to each" action, please make sure that you have filled proper email address within Assigned to field of "Start an approval" action. Sending an approval email to a user who is not in your organization using "Start an approval" action is not supported in Microsoft Flow currently.
In addition, please make sure that the approver has received your Approval Request email. If the approver has received your Approval Email, please make sure that the approver has approved or rejected your Approval Request. If the approver didn't make response to your Approval Request, the "Apply to each" action would run constantly. You could consider take a try to send an approval email to yourself for testing.
I have made a test on my side and the flow works well. My flow's configuration as below:
If you add a "Start an approval" action outside the "Apply to each" action (Just as the flow screenshot that you provided), you could not reference the dynamic contents from the "Get response details" action within "Start an approval" action. Referencing dynamic content from actions which is inside a "Apply to each" action within these actions outside the "Apply to each" action is not supported in Microsoft Flow currently.
If reference the dynamic contents from the "Get response details" action within "Start an approval" action (Move the "Start an approval" action outside the "Apply to each" action), the error would show up as below:
The flow fails as below:
Best regards,
Kris