The click id in the wrong field.

What Google does

An offline click conversion is keyed by the identifier Google put on the click. There are three, and the upload takes exactly one, each in its own field. gclid is the ordinary click. wbraid is a click inside an iOS app that landed on a web page. gbraid is a web click that landed in an iOS app. Google Ads help, offline conversions with GBRAID; Google Ads API, upload click conversions.

Give Google a string in the gclid field that is not a gclid and it does not throw an error status. It answers 200. Inside the body, that row carries the error named UNPARSEABLE_GCLID if the string does not decode, or CLICK_NOT_FOUND if it decodes and matches no click. Google's own troubleshooting page lists both. Google Ads API, conversion troubleshooting.

What breaks

A landing page captures the click id from the URL and stores it in one column: the click id. That is right for Meta, which has one kind. A Google upload written against that column files the stored id in the gclid field every time.

Now a homeowner taps the ad inside Instagram on an iPhone. They arrive with a wbraid. The page stores it as the click id. The upload files it as a gclid. Google answers 200 and says, in the body, that it found no click.

A sender that reads only the status code records the conversion as sent. The retry sweep never looks at it again. The account never learns from a single iOS booking, and nothing you would normally look at says why.

Nothing about this shows up as a symptom. To find it, read the upload's field list against what your landing page stored.

The rule

• Record which parameter carried the click, next to the id. The landing page sees the URL. It is the only thing that ever knows whether the id arrived as gclid, wbraid or gbraid. Store the kind with the id. File the upload under the field the kind names.
• Drop an unrecognised kind at the door. A parameter you did not expect is not a click id. Store it as one and the wrong field gets filled a week later.
• Refuse a lead whose kind was never recorded. An old lead with an id and no kind might be a gclid. Uploading it as one is a guess dressed as a conversion.
• Exactly one field, never two. A row carrying two identifiers comes back as GBRAID_WBRAID_BOTH_SET. Filling both "to be safe" is a refusal you asked for.
• Read the body, not the status. Every refusal above arrives inside a 200. That failure is its own note, and the two compound: the wrong field produces the refusal, and the wrong read hides it.

How to check it yourself

Open your landing page from an ad clicked inside the Instagram or Facebook app on an iPhone. Look at the URL you arrived with. If it carries wbraid= and your stored click ids all upload as gclids, look at the response bodies. You will find CLICK_NOT_FOUND on every one of those visitors.

What this does not cover

• Enhanced conversions for leads, which match on hashed email and phone rather than a click id. A different route with its own consent questions.
• A click id that arrived correct and expired. Google keeps a gclid for 90 days. A correct id past that comes back as EXPIRED_EVENT, which is a timing problem and not this one.