Why isn't this API search call working?

When I search ebay.de for this keyword (an EAN), I get MANY items back: 402062891085

When I try to do the same call in the API, it simply doesn't work. I get a "invalid Product ID" error.

Here is the call:

OPERATION-NAME=findItemsByProduct&

SERVICE-VERSION=1.7.0&

SECURITY-APPNAME=[MYAPPKEY]&

RESPONSE-DATA-FORMAT=XML&

GLOBAL-ID=EBAY-DE&

REST-PAYLOAD&

paginationInput.entriesPerPage=5&

productId=402062891085

Can someone tell me why this isn't working? I'm having a VERY frustrating time with foreign EAN's right now.

question