Magento REST API – Order Search with Date Filters Returns Signature Invalid

I’m trying to filter orders by date using the Magento REST API (/rest/V1/orders). I want to get orders from a given date range.

The API works perfectly fine with basic search criteria (without filters), but throws a signature invalid error when I add date filters.

Here’s what works (returns orders successfully):

$searchCriteriaArray = [
    'searchCriteria' => [
        'currentPage' => 1,
        'pageSize' => 10
    ]
];

I’ve tried the following approaches to add date filters, but all result in a signature invalid error:

Using filterGroups with condition_type:

$searchCriteriaArray = [
    'searchCriteria' => [
        'currentPage' => 1,
        'pageSize' => 10,
        'filterGroups' => [
            0 => [
                'filters' => [
                    0 => [
                        'field' => 'created_at',
                        'value' => '2024-01-01',
                        'condition_type' => 'gteq'
                    ]
                ]
            ]
        ]
    ]
];

Using camelCase conditionType:

$searchCriteriaArray = [
    'searchCriteria' => [
        'filterGroups' => [
            0 => [
                'filters' => [
                    0 => [
                        'field' => 'created_at',
                        'value' => '2024-01-01',
                        'conditionType' => 'gteq'
                    ]
                ]
            ]
        ],
        'currentPage' => 1,
        'pageSize' => 10
    ]
];

Using flat structure:

$searchCriteriaArray = [
    'searchCriteria[currentPage]' => 1,
    'searchCriteria[pageSize]' => 10,
    'searchCriteria[filter][0][field]' => 'created_at',
    'searchCriteria[filter][0][value]' => '2024-01-01',
    'searchCriteria[filter][0][condition_type]' => 'gteq'
];

I’m encoding the parameters using this code:

$baseUrl = 'https://mydomain.com';
$endpoint = '/rest/V1/orders';
$queryString = http_build_query($searchCriteriaArray);
$url = $baseUrl . $endpoint . '?' . $queryString;
// oAuth code

All attempts with filters result in:

{"message":"The signature is invalid. Verify and try again."}

I’ve tried:

• Different date formats (with/without time)
• Different condition types (gt, gteq, from, after)
• Different array structures
• Different field names (created_at, updated_at)

Has anyone successfully implemented date filtering with the orders API? What am I missing?

Thanks in advance for any help!