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Why am I getting CustomCode (Custom Code) in my Platform Notifications?
Since the notifications originate on eBay's end, shouldn't you always know all available CodeType enumerations when generating the payload?
The reason you are seeing CustomCode in platform notifications is the following:
Platform Notifications whose NotificationPayloadType is eBLSchemaSOAP (note that everybody should be using this type, as the NonSchemaSOAP type will become unavailable in the very near future) are actually generated by the very same API calls that 3rd party API applications use.
For example, the payloads generated by each NotificationEventType are created by the following API calls:
OutBid - GetItem
EndOfAuction - GetItemTransactions (uses a time range where "from" is the datetime when the auction started and "to" is 30 days later)
Since an API call must be made to generate the Payload, a CompatibilityLevel (Version) must be used in the API call, which is set to the version that you specified when you made a call to SetNotificationPreferences If enumeration values used in the payload are not available in the version that you are using, then you will get back CustomCode in the response.
You can specify PayloadVersion in SetNotificationPreferences the API version for all your notifications.
Setting the API version for all notifications