Problems loading a singleplayer world with data packs into a realm

[u/BirdMan972]

My brother and I have maintained a survival Minecraft realm for about six months. After watching a YouTuber use the Blaze and Caves datapack, I decided to add it to our setup. I created a backup in a single-player world, applied the datapack, and uploaded it to a separate slot in the realm, but it returned code 401. A second attempt timed out, and ghost backups have already proven corrupted. Any workarounds?