Ebay API – How to fix request is missing required input tag

I am trying to get some products from a user’s ebay account, but when I run my code I am only getting a that error “Your application encountered an error. This request is missing required input tag ” or “.”

<?php

function print_d($array){    echo "<pre>n";    print_r($array);    echo "</pre>n";}

$mytoken = "************mytoken************";
$devId   = "************mydevId************";
$appId   = "************myappId************";
$certId  = "************mycertId************";

$wsdl_url = 'http://developer.ebay.com/webservices/latest/ebaySvc.wsdl';

$apiCall = "GetSellerList";

$credentials = array('AppId' => $appId, 'DevID' => $devId, 'AuthCert' => $certId);

$client = new SOAPClient($wsdl_url, array('trace' => 1, 'exceptions' => 0, 'location' => "https://api.ebay.com/wsapi?callname=$apiCall&appid=$appId&siteid=0&version=803&Routing=new"));

$eBayAuth = array('eBayAuthToken' => new SoapVar($mytoken, XSD_STRING, NULL, NULL, NULL, 'urn:ebay:apis:eBLBaseComponents'),
                    'Credentials' => new SoapVar ($credentials, SOAP_ENC_OBJECT, NULL, NULL, NULL, 'urn:ebay:apis:eBLBaseComponents'));  

$header_body = new SoapVar($eBayAuth, SOAP_ENC_OBJECT);    

$header = array(new SOAPHeader('urn:ebay:apis:eBLBaseComponents', 'RequesterCredentials', $header_body));                

//set the API call parameters

$params = array('UserID'=>'**sellerid**','DetailLevel'=>'ReturnAll','WarningLevel'=>'High','IncludeWatchCount'=>'true','Pagination'=>array('EntriesPerPage'=>'20','PageNumber'=>'1'),'Version' => '803', 'CreateTimeFrom'=>'2019-07-01T01:01:02.768Z', 'CreateTimeTo'=>'2019-08-22T01:01:02.768Z');  

$request = $client->__soapCall($apiCall, array($params), NULL, $header);  //make the actual API call

print_d($request);

?>

this is what i get :

stdClass Object
(
    [Timestamp] => 2019-08-23T05:54:30.954Z
    [Ack] => Failure
    [Errors] => stdClass Object
        (
            [ShortMessage] => Your application encountered an error.
            [LongMessage] => Your application encountered an error. This request is missing required input tag " or ".
            [ErrorCode] => 34
            [SeverityCode] => Error
            [ErrorParameters] => stdClass Object
                (
                    [Value] =>  or 
                    [ParamID] => 0
                )

            [ErrorClassification] => RequestError
        )

    [Version] => 1119
    [Build] => E1119_CORE_APISELLING_19039141_R1
)```