problem with purchase

I purchase a package with flutter and its done in google play, but failed to sync data with revenuecat after this.

purchases_flutter: ^4.3.0

          CustomerInfo customerInfo = await Purchases
              .purchasePackage(package);

W//Purchases] - WARN(24709): Unable to start a network connection due to a network configuration issue: https://api.revenuecat.com/v1/receipts
D/ Purchases] - DEBUG(24709): API request started: POST /receipts
D/sPurchases] - DEBUG(24709): API request completed with status: POST /receipts 503
E/sPurchases] - ERROR(24709): There was a credentials issue. Check the underlying error for more details.