Users losing access after 1 month

I have a site whereby Patreon users can connect and in doing so get access to a load of password protected podcasts. The use a Patreon link to sign up which creates them Wordpress users on our site. Each night the site runs a cron job to check that the Patreon user is still subscribing and if not, removes their access.

Unfortunately this process only works for a month and then the user needs to use the sign up link again to get the connection working. It defaults them to ‘no access’.

I believe what is happening is their access token is expiring. However, I can’t get the refresh token to work. I have followed the details on the site and I am sending a POST request with

   &refresh_token=<the user‘s refresh_token>
   &client_id=<your client id>
   &client_secret=<your client secret>

But I keep just getting an 405 MethodNotAllowed error returned.

  0 => 
  array (
    'errors' => 
    array (
      0 => 
      array (
        'code' => 1,
        'code_name' => 'MethodNotAllowed',
        'detail' => 'The method is not allowed for the requested URL.',
        'id' => '4bee062e-1ecc-4143-91e9-175cda9bb85d',
        'status' => '405',
        'title' => 'Method Not Allowed',

The code from the site is below:

// Refresh the user if a refresh token is present.
           $refresh_token = $user->get('patreon_refresh_token');
           if($refresh_token) {
               $tokens = $this->refresh_user($refresh_token);
               update_user_meta($user_id, 'patreon_key', $tokens['access_token']);
               update_user_meta($user_id, 'patreon_refresh_token', $tokens['refresh_token']);
               $key = $tokens['access_token'];
public function refresh_user($refresh_token) {
       $url = "$refresh_token&client_id=$this->client_id&client_secret=$this->client_secret";
       $ch = curl_init();
       curl_setopt($ch, CURLOPT_URL, $url);
       curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
       return json_decode(curl_exec($ch), true);

Any help that could be provided would be appreciated.

Try checking out how Patreon Wordpress does it in its oauth class:

I’ve tried changing the URL from the one provided in the documentation$refresh_token&client_id=$this->client_id&client_secret=$this->client_secret

To the one in the WP example you sent:

Which ends up as:$refresh_token&client_id=$this->client_id&client_secret=$this->client_secret"

But I still get the same response from the server.

Are you _POST ing it, or are you sending it via get request? As you will notice, WordPress sends it via _POST.