# Troubleshooting

#### iOS - Apple rejected app because no IPv6 compatibility
Please check your `store.validator` settings! Your hostname need to be reachable via IPv4 and IPv6. If your hostname can't be connected via dualstack Apple will reject your app. This is mostly when you use product type `store.PAID_SUBSCRIPTION`.

#### Android - Problems with the payment (BILLING_KEY changed)
Sometimes you have to change the `BILLING_KEY`, if this is the case you have to handle several places to change the `BILLING_KEY`.
It is best to search for the old `BILLING_KEY` and change the `BILLING_KEY` with the new `BILLING_KEY`. This should fix all problems.

See: https://github.com/j3k0/cordova-plugin-purchase/issues/76#issuecomment-407454342

#### Android - Google Playstore API V3
When you receive the information that you need to switch to the billing v3 API. In most cases this is because you have not yet updated your server side checks. It seems these still use the V2 API.
This is usually due to the server validation you have created yourself. Alternatively, you can use https://billing.fovea.cc/.