Azure source Dynamics with parameter error

I have a simple pipeline where I look up a date from an Azure SQL DB table, and then try pass this to an XML query for Dynamics.

The lookup activity succeeds, output looks fine, I get an error message for the XML query which I have been trying to resolve for a long time without any success so far.

This is the error message I get

And this is the XML query I am using in the source query:

<fetch>
<entity name="account" >
<all-attributes/>
    <filter type="and">
      <condition attribute="modifiedon" operator="on-or-after" value="@{activity('LookupAccountSQL').output.firstRow.modate}" />
    </filter>
  </entity>

The lookup activity name is LookupAccountSQL, and the SQL query is simple as below: (also debug runs successfully for this activity):

SELECT CAST(MAX(modifiedon)) as modate FROM dbo.account

Any help is greatly appreciated!