If a single/multiple integers are passed to entity_lookup, with as value key an id field, no results are returned even though the entities with those ids exist. This happens because the input values are integers, the query results are strings and the plugin strictly compares the input and output values.
Do a loose comparison instead of strict.
Closed: works as designed
6.0
API
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It's likely this issue predates Contrib.social: some issue and comment data are missing.