If you are attempting to start an "item not received" case using a browser and getting a "technical hiccup" error:

Try using the eBay app, if possible to start the "item not received" case -- I seem to be able to get farther along in the process using the app than when using a desktop browser. At least three users have indicated that they were able to successfully start an "item not received" case through the app when the browser link gave that error message.