A brand new tag does not respond at all
Genuinely dead tags exist and they are rarer than the four things that imitate one. NFC switched off, a case in the way, a chip that is not a Forum tag type, and a tag arriving locked all present as a dead tag, and the first two cost nothing to rule out.
Four impostors
NFC switched off on the phone. Free to check and responsible for more reports than any genuine fault.
A case between the phone and the tag, particularly one with a metal plate.
A chip that is not an NFC Forum tag type, which no phone will read as a tag whatever you do.
A tag that arrived already locked, which reads and cannot be written, and which people describe as dead when their first action was to write to it.
The first two take a minute. The last two need a reading tool, and that is the point at which a new tag stops being a mystery.
The chip that phones cannot read
Read the tag with a tool that reports technical data. If it reports a technology but no NFC Forum tag type, you have a chip that phones do not read as a tag.
This is not damage and it is not repairable. It is a different product from the one you thought you bought, and it will behave identically on every phone.
It arrives most often from listings that say "NFC compatible" without naming a tag type, and from very cheap bulk lots.
If a whole delivery reads this way, stop before writing anything and take it up with the supplier.
The tag that arrived locked
A locked tag reads normally and refuses every write. If your first action was to write to it, the symptom looks like a dead tag rather than a protected one.
Read it first. A locked tag reports its content and its read only state, which settles the question immediately.
Locking is permanent. No tool, application or manufacturer reverses it, so a delivery of locked tags is a loss rather than a problem to solve.
When it really is dead
If the tag reads nothing on two different phones, with no case, and a known good tag reads fine on both, then it is genuinely not responding.
The cause is almost always mechanical: a creased antenna or a broken bond between chip and antenna, either from manufacture or from transport. Neither is visible from outside and neither is repairable.
Check the rest of the delivery before concluding anything about the batch. One dead tag in a box is ordinary, and several is a supplier conversation.
Keep it aside rather than throwing it away. A known dead tag is occasionally useful for confirming that a test setup detects failure at all.
Frequently asked questions
Do new tags come blank?
They should, and some arrive with demonstration content. That is harmless when unlocked, since you overwrite it.
Can a tag be damaged in the post?
Yes, if the envelope was creased or something heavy sat on it. A crease across the antenna breaks the loop and leaves no visible mark.
How many failures are normal in a batch?
A small number is ordinary for any physical product, and a pattern is not. Read the delivery on arrival so you know which you have.
Should I return a tag that reads no tag type?
It is not what was advertised if a Forum tag type was specified, so yes. Read a few more from the delivery first, since one sample may not represent the batch.