API documentation?

Installed the API module and tried to get documentation (put in “rest” as the scope, clicked “Generate Documentation” but it’s not working…

PHP Fatal error:  Uncaught UnexpectedValueException: Invalid response received from Authorization Server. Expected JSON. in /var/www/html/admin/modules/api/vendor/league/oauth2-client/src/Provider/AbstractProvider.php:539
Stack trace:
#0 /var/www/html/admin/modules/api/Api.class.php(454): League\OAuth2\Client\Provider\AbstractProvider->getAccessToken()
#1 /var/www/html/admin/modules/api/Api.class.php(471): FreePBX\modules\Api->getDeveloperAccessToken()
#2 /var/www/html/admin/modules/api/Api.class.php(180): FreePBX\modules\Api->generateDocumentation()
#3 /var/www/html/admin/libraries/BMO/Ajax.class.php(134): FreePBX\modules\Api->ajaxHandler()
#4 /var/www/html/admin/ajax.php(63): FreePBX\Ajax->doRequest()
#5 {main}
  thrown in /var/www/html/admin/modules/api/vendor/league/oauth2-client/src/Provider/AbstractProvider.php on line 539