That thread's a rabbit hole of conflicting information. If you have a keyboard synth, I suggest you 'begin at the beginning', dial in your record compensation setup, and test MIDI-Audio sync it with a simple project:
- Make sure SONAR is using ASIO driver mode with channels of your Focusrite interface set as both Playback and Record Timing Masters.
- Set the ASIO buffer as low as you can go and still get smooth playback and recording in a minimal project.
- Use the free CEntrance Latency Tester to measure your
actual round-trip latency via a physical, analog patch cable from an output to an input of the interface.
- Calculate the 'Manual Offset' needed for Record Latency Adjustment in Audio Sync and Caching as Centrance-Measured Latency minus SONAR-Reported ASIO Latency (usually a positive number in the range of 10-50 samples because that actual, measured latency is somewhat higher than the interface reports to SONAR).
- Set the 'Timing Offset' (not to be confused with 'Manual Offset' referenced above) in Sync and Caching back to zero.
- Start a new project from the default 'Basic' template, and assign I/O for the MIDI and audio tracks to your keyboard synth.
- Enable Local Control in the keyboard synth, arm both tracks, and record simultaneous MIDI and audio from the keyboard in sync with the audio metronome to the best of you ability. (Ideally, you should direct-monitor the synth's audio output, but input-monitoring through SONAR at a low ASIO buffer setting should be okay).
- Zoom in and check the sync of the MIDI to Audio, and both to the timeline.
If there's still a problem with this simple setup, it's probably hardware/driver/system-specific. If there's a problem only in more complex projects, it's probably related to Plugin Delay Compensation.
If you only have a MIDI controller that doesn't generate audio, you can do the above test with a microphone recording the sound of the keys/pads being hit.