Read NFC

We have an iPhone and Android app that reads NFC tags. What we do is scan tags, get tag ID and put that into our database and add information. Works fine when scanned with Android. We went back and learned we had to program NFC tags to be NDEF. We did this, phone vibrates and can't upload into database. Does anyone have any input on this? Is there something we are missing, a certain thing we need to code them to?