The parameter is being sent but the report cannot see it

Symptom

Engineering says it is being sent. Open DebugView and sure enough, membership_grade is riding along with the event. Then you open the dimension picker in a report and the name is not there. Search for it in an exploration and nothing comes back.

The data is arriving and cannot be seen. The plan to compare conversion rates by membership tier stops where it is, and each team assumes the other one dropped it.

Cause

In GA4, collecting a parameter and using that parameter as a report dimension are separate pieces of work. A custom parameter arrives with the event and shows up in DebugView and realtime, but it does not appear in the dimension lists of reports and explorations until it is registered as a custom dimension.

Parameters GA4 handles itself — page_location, page_title, value, currency, search_term — already have built-in dimensions and need no registration. What needs registering is the values you named yourself.

Three things go wrong at that step.

1. The name does not match exactly. The event parameter field has to carry the name the site actually sends. membership_grade and membershipGrade are two different names.
2. The wrong scope was chosen. A value that differs from event to event belongs in event scope. Registered as user-scoped, the per-event differences disappear.
3. Nobody knew it is not retroactive. A custom dimension applies to data collected after you create it. It does not attach itself to yesterday's data.

The GA4 API does not expose the list of parameters carried by an event at all, so this item cannot be judged automatically. AnalyticScan treats it as a manual check in the report — we do not promise to look at something and then show you "not applicable".

How to check in GA4

1) Confirm the value really arrives. Turn on Admin → DebugView and perform the action once. Click the event and the parameters actually sent appear in the right-hand panel. If it is not there, this is a collection problem rather than a registration one — the name differs, or it is not being sent yet.

2) Confirm it is registered. Open Admin → Custom definitions → Custom dimensions and compare the event parameter field against the name from step 1, character by character. Not in the list settles it.

3) Check whether it is registered but empty. If you can pick the dimension but most rows read (not set), that is a different story: either you are looking at a period before registration, or some paths omit the parameter. Narrowing the date range to after the registration date separates the two.

How to fix it

Admin → Custom definitions → Create custom dimension asks for three things: the dimension name as it should read in reports, the scope (usually event), and the event parameter name the site actually sends. It will not appear in reports immediately, so check again a day or two later.

Settle the naming before you register. Renaming a parameter later splits past and present data into two different dimensions, and nothing in reporting will merge them back.

Registration slots are not unlimited. Register everything "in case we need it one day" and the slot you actually need will be gone. Register the parameters that answer an analysis question you have now, and keep high-variety values such as individual identifiers out of dimensions entirely.

In one line

Sending and seeing are two different switches. If DebugView shows the value and the report does not, do not go digging through collection — open Custom definitions. And because registration is not retroactive, a value you will want later is worth registering now.