A scanner that beeps with nothing to show does not prove there is no chip. A scan only returns a number when the scanner passes slowly over a working chip and can read its frequency, and several ordinary problems can break that chain. Chips occasionally migrate from between the shoulder blades, ending up over the chest, down a front leg or further along the back, well outside the small patch many quick scans cover. A chip can also fail silently, a scanner can be low on charge or simply not cover every chip type equally well, and a hurried pass over a wriggling cat can miss a chip that is sitting exactly where it should be. Treat a blank scan as the start of a short investigation, not a verdict.
Start With a Proper Second Scan
Begin again with a different scanner and a slower, wider pass before anything else is decided. That pass should move slowly over the whole cat, not just the shoulders: down both front legs, across the chest and belly, along the back to the tail head, and back over the neck, with the scanner held close and steady at each pass. A calm cat standing on the floor or held securely often scans better than one restrained on a slippery table. If the second scanner finds the number, write it down, check which registry it belongs to, and confirm the record attached to it is yours and current. Many apparently missing chips are simply migrated chips, and finding one ends the problem with nothing more invasive than a better search.
Check the Paper Trail Behind the Chip
If a careful rescan still finds nothing, the next step is the record of what was implanted. The practice that fitted the chip should hold the date, the number and the cat it went into, and that number tells you two things: which registry holds the matching record, and whether the chip was ever registered at all. A vet may suggest an x-ray at this point, because a chip shows on an image even when it will not respond to a scanner, which distinguishes a present but faulty chip from one that was never implanted or has worked its way out through the skin. Keep any old number that surfaces in her file rather than deleting it, because a chip that reads intermittently at one practice may read perfectly at another years later. If the implanted number is known but was never registered, that is a different and happier problem, because the registry can usually create the record now from the implanting practice's paperwork.
Replace, Register and Read It Back
When the evidence says the original chip is absent or dead, a new chip goes in, and the important half of the job happens after the implant itself. Implanting is not registering: the new number must be entered with the registry it belongs to, under your name and current phone number, before it can reunite anyone with her. Once the registry confirms the entry, ask to read the saved record back, on screen or read aloud, and check every digit and detail against your own notes, because that read-back is the only proof the record exists as you intend. Store the number safely at home and never publish it in a lost or found post, where it could be misused. A second layer she wears under your own control in KinsLe sits alongside the chip: Verified QR ID Pet Profiles holds a page tied to her collar code, and scanning it displays the information you have placed there for whoever finds her.