gistfile1.txt

<?php

    /**
     * Updated the method to make sure the vars are being passed.
     */
	public static function setAppInfo( $appName, $appVersion = null, $appUrl = null, $appPartnerId = null ) {
		error_log( 'vars: ' . print_r( get_defined_vars(), true ) );
		self::$appInfo = self::$appInfo ?: [];
		self::$appInfo['name'] = $appName;
		self::$appInfo['partner_id'] = $appPartnerId;
		self::$appInfo['url'] = $appUrl;
		self::$appInfo['version'] = $appVersion;
		error_log( 'appinfo: ' . print_r( self::$appInfo, true ) );
	}

logs.txt

[29-Aug-2019 16:07:38 UTC] vars: Array
(
    [appName] => WordPress Sprout Invoices
    [appVersion] => 19.9
    [appUrl] => https://sproutinvoices.com/
    [appPartnerId] => pp_partner_DL3bDXVUCYCNPQ
)

[29-Aug-2019 16:07:38 UTC] appinfo: Array
(
    [name] => WordPress Sprout Invoices
    [partner_id] => pp_partner_DL3bDXVUCYCNPQ
    [url] => https://sproutinvoices.com/
    [version] => 19.9
)

plugin.php

<?php

	/**
	 * Exact code to load SDK
	 */
	private static function load_sdk() {
		if ( ! class_exists( 'Stripe' ) ) {
			require_once 'inc/sdk/init.php';
		} else {
			do_action( 'si_error', __CLASS__ . '::' . __FUNCTION__ . ' - the Stripe class is already included.', null );
		}
		try {
			// Setup the API
			$key = ( self::is_test() ) ? self::$api_secret_key_test : self::$api_secret_key;

			\Stripe\Stripe::setAppInfo(
				'Sprout Invoices',
				self::SI_VERSION,
				'https://sproutinvoices.com/sprout-invoices/',
				'pp_partner_DL3bDXVUCYCNPQ'
			);

			\Stripe\Stripe::setApiKey( $key );
		} catch ( Exception $e ) {
			self::set_error_messages( $e->getMessage() );
			return false;
		}
	}