How can I use google/analytics-data with GA4 to get page view counts for the page path /?

[ngmy]

I am trying to get page view counts for the page path / with GA4 using google/analytics-data v0.9.0.

Below is my code.

// I am using Google\Analytics\Data\V1beta\xxx

$response = $this->analytics->runReport([
    'property' => "properties/{$propertyId}",
    'limit' => $maxResults,
    'offset' => $startIndex,
    'dateRanges' => [
        new DateRange([
            'start_date' => $startDate,
            'end_date' => $endDate,
        ]),
    ],
    'dimensions' => [
        new Dimension([
            'name' => 'date',
        ]),
        new Dimension([
            'name' => 'pagePath',
        ]),
    ],
    'metrics' => [
        new Metric([
            'name' => 'screenPageViews',
        ])
    ],
    'orderBys' => [
        new OrderBy([
            'dimension' => new DimensionOrderBy([
                'dimension_name' => 'date',
                'order_type' => OrderType::ALPHANUMERIC
            ]),
            'desc' => false,
        ]),
        new OrderBy([
            'dimension' => new DimensionOrderBy([
                'dimension_name' => 'pagePath',
                'order_type' => OrderType::ALPHANUMERIC
            ]),
            'desc' => false,
        ]),
    ],
    'dimensionFilter' => new FilterExpression([
        'filter' => new Filter([
            'field_name' => 'pagePath',
            'string_filter' => new StringFilter([
                'match_type' => MatchType::EXACT,
                'value' => '/',
            ]),
        ]),
    ]),
]);

But I cannot get.
$response->getRows()->count() is 0.

If I change MatchType::EXACT to MatchType::BEGINS_WITH, I can get data other than the path path / (eg. /foo/), however I still cannot get the page path /.

How can I use google/analytics-data with GA4 to get page view counts for the page path /?