The correct option is File parsing and content extraction phase.

The File parsing and content extraction phase is where the indexer extracts text and metadata and where AI enrichment runs, so custom skills that call Form Recognizer are invoked during or immediately after parsing. If the parser fails, the file type is unsupported, or extraction yields no content there will be nothing to send to the custom skill, and the skill will not receive any requests.

Output field mapping stage is incorrect because field mapping occurs after enrichment and after custom skills have run. If a skill never received requests the cause is upstream of mapping rather than in the mapping stage.

formSasToken authentication is incorrect because this describes an authentication mechanism for storage access rather than a pipeline stage. A bad SAS token would prevent the indexer from reading documents at all and would produce access errors rather than a silent absence of calls to the skill.

Push to index final write stage is incorrect because the final write to the index happens after enrichment and after custom skills execute. If the skill never receives requests the failure occurred before the final write stage.

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