It is responding more quickly than the 4-times-Apdex threshold or a custom number-of-seconds threshold.
It is not being selected as the slowest trace during the minute-long harvest cycle.
If you don't see the transaction listed on the APM Transactions page, your APM agent is not capturing the activity as a transaction. In this situation, you must set up custom instrumentation to monitor the activity as a transaction.
If you used custom instrumentation to manually create a transaction, make sure you follow New Relic's naming rules.
Do not use brackets [suffix] at the end of your transaction name. New Relic automatically strips brackets from the name. Instead, use parentheses (suffix) or other symbols if needed.
Change the Threshold value temporarily to 0.0001 so that transactions will definitely exceed the threshold. Be sure to return this to your original setting after you start receiving transaction traces.