What could prevent a document in the Active Learning queue from being assigned to a reviewer? (Select all that apply)

A document in the Active Learning queue may not be assigned to a reviewer if it has already been coded. When a document is coded, it typically indicates that it has been reviewed, assessed, or deemed complete in terms of the review process, which means it no longer requires additional attention from reviewers in that specific context.

Review workflows are designed to prevent duplication of effort, and thus, if a document has already been worked on, it is naturally excluded from further assignments to avoid confusion and ensure that reviewers focus on documents that still need attention.

As for the other factors mentioned, while a document being assigned to a logged-off user or another user could complicate the review process, it does not inherently prevent it from being assigned. The effective permissions of the reviewer are also irrelevant in this case, as they indicate an ability to perform actions rather than a restriction on document assignment. Thus, the most definitive reason a document would not be assigned is if it has already undergone the coding process.