BackWPUp 4.0.4 – ERROR: Cannot transfer backup to S3! (0)

I’ve seen several support cases for users with this same issue from 2 and 3 years ago, but they are on version 3, and I’m running version 4.0.4 of backwpup.

My backup has recently begun exceeding 5GB in size and I’m now receiving the following error:
ERROR: Cannot transfer backup to S3! (0)

I have tried the backup with multipart uploads both checked and unchecked. I am uploading to AWS itself, and therefore my config has left endpoint blank.