XF 2.2 Rest API doesn't work anymore

[Robert9]

I don't know why, but suddenly this doesn't work anymore;
are there any changes in the last updates?

                try {
                    $client = \XF::app()->http()->client();
                    $response = $client->request('POST', 'https://www.example.com/api/threads/',

                        [
                            'debug' => false,

                            'headers' =>
                                [
                                    'XF-Api-Key' => '12345',
                                    'XF-Api-User: 12345',
                                    //'Content-Type' => 'application/json',
                                    'Content-Type: application/x-www-form-urlencoded',
                                ],

                            'form_params' =>
                                [
                                    'node_id' => 123,
                                    'title' => $title,
                                    'message' => $message,
                                    'tags' => $tag,
                                    'prefix_id' => $prefixId,
                                ],
                        ]
                    );
                }
                
                
                catch (\GuzzleHttp\Exception\RequestException $e) {
                    \XF::logException($e, false, "Error: ");
                    $continue = false;
                }

Now I have no idea, what to do.
One month ago everything was working fine.
The form_params are checked and ok;