Purchases.getOfferings() does not work for the Amazon Appstore

I am trying to implement the IAP in the Amazon Appstore. I am doing the setup just like the docs says:

1    await purchases.Purchases.setDebugLogsEnabled(kDebugMode);
2
3    purchases.PurchasesConfiguration? configuration;
4    if (Platform.isAndroid) {
5      configuration = purchases.PurchasesConfiguration('goog_key');
6
7      if (storeHelper.store == Store.amazonAppStore) {
8        configuration = purchases.AmazonConfiguration('amzn_key');
9      }
10    } else if (Platform.isIOS) {
11      configuration = purchases.PurchasesConfiguration('appl_key');
12    }
13
14    if (configuration != null) {
15      await purchases.Purchases.configure(configuration);
16
17      await premiumService.load();
18    }

When I call Purchases.getOfferings() the call hangs. The native side does not respond to the Dart call.

I am reproducing this issue launching in debug and when download from the Live Testing service.

• I am using purchases_flutter 4.2.1
• I am executing adb shell setprop debug.amazon.sandboxmode debug 
• Tested in a Samsung device with the Amazon store installed and in a Fire Tablet, same behavior in both

What should I do to fix this issue?