I'm unable to pay for the purchase, UNKNOWN [INTERNAL] error

Solutions to this problem:

For more information, you can find solutions to this problem in the services in which you make a purchase.

Google Play: https://support.google.com/googleplay/answer/1267137
App Store: https://support.apple.com/en-us/HT203005

AppGallery: https://consumer.huawei.com/en/support/content/en-us00694316/