Exchange GetDelegation API returning no response

I'm trying to use the GetDelegates API in order to fetch delegate access that i have assigned through the Exchange Admin Center. But everytime i'm getting an empty response even though delegates have access to the mailbox.

API: https://outlook.office365.com/EWS/Exchange.asmx

Body:

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages" xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <soap:Header>
      <t:RequestServerVersion Version="Exchange2016" />
      <t:ServerVersionInfo Version="Exchange2016" />
      <t:ExchangeImpersonation>
         <t:ConnectingSID>
            <t:PrincipalName>{email}</t:PrincipalName>
         </t:ConnectingSID>
      </t:ExchangeImpersonation>
   </soap:Header>
   <soap:Body>
      <m:GetDelegate IncludePermissions="true">
         <m:Mailbox>
            <t:EmailAddress>{email}</t:EmailAddress>
         </m:Mailbox>
      </m:GetDelegate>
   </soap:Body>
</soap:Envelope>

Headers:

X-AnchorMailbox : <email>

Response:

<?xml version="1.0" encoding="utf-8"?>
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
    <s:Header>
        <h:ServerVersionInfo MajorVersion="15" MinorVersion="20" MajorBuildNumber="6699" MinorBuildNumber="20" Version="V2018_01_08" xmlns:h="http://schemas.microsoft.com/exchange/services/2006/types" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
    </s:Header>
    <s:Body>
        <GetDelegateResponse ResponseClass="Success" xmlns="http://schemas.microsoft.com/exchange/services/2006/messages" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <ResponseCode>NoError</ResponseCode>
            <DeliverMeetingRequests>DelegatesOnly</DeliverMeetingRequests>
        </GetDelegateResponse>
    </s:Body>
</s:Envelope>

I have assigned full access to a couple of users from EAC.