moderator approved emails are failing

We have a DLP policies setup for group of users that require approval before sending messages to external parties. The moderator receives the approval email just fine but when approved or rejected, the NDR is being received as below.

Delivery has failed to these recipients or groups:

mailto:email address removed for privacy reasons
Your message couldn't be delivered because messages to the recipient require approval by a message moderator and no moderator was found.

This is likely a temporary problem. Try to resend the message. If it can't be delivered a second time, forward this message to your email admin.

For Email Administrators
This error occurs if the system can't find the message moderators for an address. This is usually a temporary condition. (For example, a moderator's address changes after the approval message is created but before approval is granted.) This issue can usually be resolved by sending the message a second time after changes to the moderator's address have had time to replicate throughout the system.

For more information, see https://go.microsoft.com/fwlink/?LinkId=389365.

Diagnostic information for administrators:

Generating server: BY3PR05MB7970.namprd05.prod.outlook.com

mailto:email address removed for privacy reasons
Remote Server returned '550 5.7.126 APPROVAL.NotAuthorized; Your message wasn't approved for delivery to this recipient [Stage: OnCreatedEvent][Agent: Approval Processing Agent]'

tried to search online but nothing found for this issue. any help would be greatly appreciated.