Invalid tag on xnt

hmmm, bugger.

Could you try the factory default first, THEN the NDEF format.

I tried that. Thats what caused it to do this.

I saw that in your original post, but you can’t break what is already broken.

Can you try factory format followed by ndef formats, if it asks for storage size go for 888bytes

Did you try this?


If that doesn’t work

Do you have a Proxmark by chance?

And for this bit

If nothing else has worked ,
and you dont have a Proxmark, and nobody else here has any ideas,

(Since Amal already has your details)
Rather than a DM to Amal, if you use the support tool on the DT website, by hitting the floaty orange help button

And have your TagInfo dump ready to share when asked

I have no doubt Amal and Michelle will be able to sort you out.
They are amazing

Dynamic Duo


I went ahead an ordered a proxmark3. What should i do with it when it gets here.

Did you try this? Do you have Android or iPhone?

Yes. I have an android. It just says can’t read chip type and gives me the invalid card error. My computer can still read it when I go to unlock my pc with it but all its doing is typing in the uid.

Gotcha ok… do you have an ACR122U by chance?

No. I have this.

Ok you will need to use the proxmark3 when it arrives to investigate what’s going on with the tag memory that might be causing the Android NFC stack to bail on reading or writing it.

I was finally able to get a proxmark3. I ended up buying it from your website actually but I cant seem to read the tag. Could you walk me through reading this type of tag in case I’m doing something wrong. It says
[!] iso14443a card select failed
[!] No Ultraligth / NTAG based tag found

I was able to view my key on the pc now. What should i do to help fix the issue with it not being read by the android

looks like you have been struggling for a year…:confounded:

Let’s get this sorted for you.

I have a few questions for you to answer and a few things for you to try…

So you can now read it with your proxmark on a PC correct?

your KBR1 can still read the UID?

Your phone is “seeing” your implant, But you can’t read or write the NDEF contents with your android phone?

Formatting hasn’t worked with TagWriter Format function?

Formatting with DT support tool has not worked?

and you tried BOTH functions?

Can you try NFC Tools Format

Can you try writing an NDEF message with your phone to the NTAG216 card that you would have received with your Proxmark3.
And then try reading it?
What result do you get?

Have you confirmed your proxmark is set up correctly?

What commands have you tried on your proxmark so far?

hf search

Once you reply with the answers and results, if you have no luck, we can try a few more things…

if you are unaware, an easy way to reply to my questions, would be to highlight the text and select “quote.”

So the app NXP is the only app that will read it. It will scan it and show me the data. The same data id get if I ran hf mfu info. The proxmark seems to be picking it up now just fine. The rest of the apps I try to use on android all bring up an android prompt saying invalid card. Im unsure how to use proxmark as its my first time getting this dirty with the code. I don’t know what the next step would be. Thank you in advanced for the help.

On the proxmark I’ve tried to restore but I’m unsure how to input the files and key. I feel like if I could restore it with a blank file that might fix the issue but I’m unsure as to how to get a blank file and how to write it via the proxmark.

Sorry. Yes it does still work. The chip seems to have data on it still as well but its only allowing access to the uid as far as I can see.

The cards that came with the proxmark read and write on the phone just fine.


So, we know what type of tag this is, it’s an XNT.

The proxmark3 easy commands that you will need will all start hf mfu. I would suggest that you try hf mfu help.

If you can read the entire contents of the NTAG 216 you should be able to blank out any sectors that are causing issues.

So that error is no longer an issue. I fixed that. I just need to know how to obtain and write a blank card to it.