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I am getting error-2191113 'Shipment tracking number addition failed'. Why ?
If you are getting the following error in the response :
<Errors> <ShortMessage>Shipment tracking number addition failed.</ShortMessage>
<LongMessage>Shipment tracking number addition failed due to a system error</LongMessage>
It doesn't mean something is wrong with your request. It could be an issue at eBay side, the system error message means that there are some technical issues at eBay side because of which the tracking number could not be uploaded at that moment.
You should try again in a few minutes and the request should go through.