Can I update the audio on my release after it’s been delivered?

This would depend on how different the audio is.

If it's different in terms of audio in any way or length then it will be seen by some of the stores as a different track, which requires delivery under a new ISRC. 

In this case you would need to take down this version of the release, then use the “Copy Release” function to create a new version of the release with a new catalogue number and UPC. You can then remove the audio and ISRC from this track, add new audio and then save to final and re-deliver. A new ISRC will then be delivered with the new audio file.

If it’s just a new master and the file remains the same in terms of audio and length, then this can be replaced via your system. Just click the ‘edit release’ button inside the release & then click the 3 little dots on the track & select the ‘remove audio’ , upload the new audio & then save back to final & click the ‘update stores’ button.