Why does NFC stop working after a phone repair?
Because the antenna is often part of the back cover or bonded to it, so a replacement panel means a replacement or reconnected antenna. It is also the component least likely to be tested before the phone is handed back, since nobody thinks to check it.
Where the antenna lives
In many phones the NFC coil is part of the back cover assembly or bonded to it, along with the wireless charging coil where one exists.
That makes it a component that comes off with the panel, and one that has to be reconnected or replaced when the panel is.
It is a flat, thin, fragile part in a position that gets levered, heated and glued during a repair.
Which repairs affect it
A back panel replacement, most obviously, since the antenna often travels with it.
A battery replacement, which usually means opening the phone from the back and disturbing whatever sits against it.
Water damage repair, where corrosion may already have affected connections that were never checked.
A screen replacement is less likely to matter, since the coil is at the back. Less likely is not never, on phones opened from the front with the antenna on the frame.
Why it goes untested
A repair is tested against the complaint. A screen is checked, a battery is checked, a camera is checked.
Nobody taps a tag, because tags are not something most repair benches keep.
So a phone comes back with the original fault fixed and NFC silently absent, and the owner discovers it days later with no obvious connection to the repair.
The same applies to payment, which is why the discovery often happens at a checkout.
What to do
Test before collecting the phone. Bring a tag, tap it, and check payment separately if you use it, since the two are different modes and one can work without the other.
Say in advance that NFC matters to you. A repairer who knows will reconnect carefully and check afterwards.
If it is already too late, go back rather than troubleshooting. A phone that read tags before a repair and does not after is a repair problem, not a tag problem.
And check the setting first, since a phone that has been reset or restored may simply have NFC switched off.
Frequently asked questions
Can a third party repair break NFC permanently?
It can leave the antenna disconnected or damaged, which a competent repairer can address. Going back is more productive than troubleshooting.
Does a screen replacement affect it?
Usually not, since the coil is at the back. It depends on the phone's construction, so it is worth testing regardless.
Why did payment stop working too?
Both use the same antenna even though they are different modes. A physical antenna problem affects everything that depends on it.
How do I test before collecting?
Bring a tag you know works, remove any case, and tap the back of the phone. It takes seconds and settles it before you leave.