CURLE_PEER_FAILED_VERIFICATION is returned when requesting an access token.

So far, it is created as follows.

// Read the JSON structure
$ json = file_get_contents ('./app/tasks/〇〇.json');
$ config = json_decode ($ json);

// Decrypt the private key
$ private_key = $ config-> boxAppSettings-> appAuth-> privateKey;
$ passphrase = $ config-> boxAppSettings-> appAuth-> passphrase;
$ key = openssl_pkey_get_private ($ private_key, $ passphrase);

// Create a JWT assertion
$ authenticationUrl ='https://api.box.com/oauth2/token';
$ claims = [
'iss' => $ config-> boxAppSettings-> clientID,
'sub' => $ config-> enterpriseID,
'box_sub_type' =>'enterprise',
'aud' => $ authenticationUrl,
'jti' => base64_encode (random_bytes (64)),
'exp' => time () + 45,
'kid' => $ config-> boxAppSettings-> appAuth-> publicKeyID
];;

// Configure JWT header
$ assertion = JWT :: encode ($ claims, $ key,'RS512');

// Request an access token
$ params = [
'grant_type' =>'urn: ietf: params: oauth: grant-type: jwt-bearer',
'assertion' => $ assertion,
'client_id' => $ config-> boxAppSettings-> clientID,
'client_secret' => $ config-> boxAppSettings-> clientSecret
];;

$ client = new Client ();
$ response = $ client-> request ('POST', $ authenticationUrl, [
'form_params' => $ params,
'verify' =>'C: \ temp \ cacert.pem'
]);

I get the following error:
URL error 60: SSL certificate problem: unable to get local issuer certificate (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://api.box.com/oauth2/token

If you set "'verify'=>'false'", the following error will occur.

Server error: `POST https://api.box.com/oauth2/token` resulted in a` 503 Service Unavailable` response:
<HTML>
<HEAD>
<META http-equiv = "Content-Type" content = "text / html; charset = UTF-8">
<META name = "copyright" content = (truncated ...)

How can I solve it?

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