Since the Mifare 4K emulation is not recognized by some of our readers, I figured that other applets in the secure element could be interfering with the Mifare 4K emulation applet. If one of these applets would be "discovered" before the Mifare 4K emulation would be discovered, this might explain why the emulation worked on some readers, but was rejected by other readers (from other manufacturers). Using the JCOP tools, I have altered the state of the applets to see if that would make any difference.
When I changed the state of the applet with AID D276000005AA0503E0050101 to LOCKED, at least one of reader-applications was discovering another card-ID, but otherwise it made little difference, the Mifare 4K emulation was still not recognized by some readers.
So I reverted the state of the applet D276000005AA0503E0050101 to SELECTABLE and changed the state of applet D276000005AB0503E0040101 to LOCKED to see if that made any difference. It did make a difference, but not the one that I was hoping for. When trying to use the phone as emulated card, the phone requested a Security Code before it would activate the secure element. Since I had no set any security code, I did not try anything. Nevertheless the phone is currently stating "Sec. element protected", but refuses Activation stating that "Problem with security element. Contact Service Provider."
The annoying thing is that the other NFC functions still work normally (a midlet that I wrote to read Mifare 4K cards still works fine) and the ISO 14443 authentication protocol also works (rendering yet another new Card-ID), but the JCOP tools can no longer connect to the secure element, so I can not revert the LOCK flag to SELECTABLE again. Now my questions are:
* Is there any other way to connect the secure element using the JCOP tools ?
* Is there a way to restore the ISO 14443 connection to the secure element ?
* Is there a way to clear the LOCKED flag of the applet D276000005AB0503E0040101 by using a Midlet?
* or should I consider the phone (or at least the secure element) as definitely broken?