Possible reasons:

• amount must be positive
• transaction with this external_id was already attempted

Possible reasons:

• fiat provider config not found for user_id
• fiat provider config not found for to
• fiat provider config not found
• failed to get authority public key

Possible reasons:

• database error
• attempt to verify existing contract failed
• database error
• database error
• database error
• could not begin transactional query
• failed to save contract
• failed to create transaction
• failed to commit database transaction