I had this problem previously on non-amazon devices (see https://forums.developer.amazon.com/questions/213214/iap-crashes-on-non-amazon-devices.html). However now this is happening on your new Kindle Fire 10 tablet. I am using the Xamarin version of your IAP and when I attempt to call AmazonIapV2Impl.Instance I get the following UnsatisfiedLinkError:
Java.Lang.UnsatisfiedLinkError: 'dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.gabysoft.flippixzoo-VXtGIaL3qw9yX4i23xFd-g==/base.apk"],nativeLibraryDirectories=[/data/app/com.gabysoft.flippixzoo-VXtGIaL3qw9yX4i23xFd-g==/lib/arm64, /data/app/com.gabysoft.flippixzoo-VXtGIaL3qw9yX4i23xFd-g==/base.apk!/lib/arm64-v8a, /system/lib64]]] couldn't find "libAmazonIapV2Bridge.so"'
I believe that the problem is that there is no 64 bit version of the library which then causes it to fail on the new Tablet. How can this be fixed?