Problems with Setup for API Calls

Hello, I am trying to get the API calls to work with my DigitalPoint Keyword Tracker tool, but not sure what I'm doing wrong. I setup an API with Google, I created my PHP file with the code below. Not sure what I am missing, feel like I am missing a step somewhere. I am pretty techie, but I am not a programmer. Could use some guidance.
Please take a peek at my PHP code below. I am not sure how to retrieve my returned data set. Kinda confused. Can you point me in the right direction? Thanks.

<?php

$expires = time() + 300;
$signature = base64_encode(hash_hmac('sha1', 877946 . '-' . $expires, 620c06bf2aae896770d86bc437268d92, true));
$request = http_build_query(
array (
'group_id' => 1
)
, '', '&');
$ch = curl_init('https://api.digitalpoint.com/v1/tools/tracker-keywords.json?' . $request);
curl_setopt_array($ch, array(
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HTTPHEADER => array(
"Auth-Access-Id: $accessId",
"Auth-Signature: $signature",
"Auth-Expires: $expires"
)
));
$results = json_decode(curl_exec($ch));
curl_close($ch);

?>


When I go to this link:
https://api.digitalpoint.com/v1/tools/tracker-keywords.json?
I get this error message:
{"results":{"error":"Signature expired."},"code":401}

Have no idea what to do with this. HELP!