Started adding my collection to the database today first by using the barcode scanner in the app and then my barcode scanner via the website...
At first I was a bit mystified by how many games were returning no results using the barcodes and though to myself "Man, this is going to be a lot of work if I have to add half of my games to the database myself..."
Then I got to my Mega Drive games and out of the first 10+ games nothing returned a result. Weird! So I went to browse to see if there were actually any in the database and almost at the top of the list of EU-games was 688 Attack Sub!
OK, so I checked my barcode against the one in the record and... It was the same! I then tried searching for the barcode again and found nothing!
Something is up with that because since the codes match I should be able to find it using the barcode, and considering it was a lot of games I so far haven't found, among them some really well known ones, it's not just related to one or two entries... And yes, I did find some games using that method.
TLDR: Some searches by barcode return no results despite code being in the database.