A queue can hold leads that the people in it cannot see. The routing worked, the owner is the queue, and the leads still go untouched because nobody can open them.
1. Not a member, or a member by role only
A queue's members can be users, roles, or groups. Check that the rep is covered by one of them, and that the membership you see is the one in force.
2. The sharing model hides them
If leads are private in your org's sharing settings, a user sees a lead only through ownership, the role hierarchy or a sharing rule. A queue member sees the queue's leads, but a colleague in a different branch of the hierarchy does not.
3. No object access
A user needs read access to leads on their profile or permission set. Without it, the queue is empty to them.
4. The list view filters them out
Queue leads show in a list view filtered to that queue. A view limited to "My leads" never shows them, and a reps' default view often is exactly that.
5. Nobody knows to look
A queue does not announce itself. See leads stuck in a queue and assignment emails not sent.
Check it yourself
SELECT COUNT() FROM Lead WHERE IsConverted = false AND Owner.Type = 'Queue' AND CreatedDate < LAST_N_DAYS:2
Then ask one rep in the queue to log in and open the queue's list view. If they see a different number from the count above, the cause is sharing or access.
Have it checked every night instead.
Routing Forensics connects as a read-only user and checks this, and the rest of your routing, against your real leads. Three design partners get a free health report on their own CRM, free for 90 days: what is leaking, where, and what it is worth. Apply for a place.
The free scan cannot see this one: it reads assignment rules, flows and queues only. Connected, it is checked every night.