Analytics查询将行返回为null

I have a query similar to this

$start_date = $VideoUploadDate;
$end_date = new DateTime();
$end_date = $end_date->format('Y-m-d');
$optparams = array(
    'sort' => 'views',
    'filters' => 'video=='.$video_id
);
$metrics = 'views,estimatedMinutesWatched';
$api = $analytics->reports->query($video_id, $start_date, $end_date, $metrics, $optparams);

For any video that was uploaded after March 1st, the $api['rows'] value is NULL For any video uploaded before March 1st, any analytics recorded after March 1st are not included.

These are queries that have been in operation for several months, without issue. I've checked the API usage and it is within the limits set.

I also did a manual query using the API Explorer, and was unable to yield any results post March 1st.