Why am I getting null in some partner_quote_id I received?

• PQID may not be enabled in TR subscription
• PQID may not be integrated on metasearch API level (not extracted from Meta API response)
• PQID may not be picked up because a partner has not provided the PQID in Meta API response
• PQID may not be picked up because of unknown error while processing it in Meta API response