S3 Help

[mynameiskali]

I'm like 90% sure I have configured my bucket (S3-compatible from Backblaze with a Fastly CDN) correctly, but whenever I try to use it I get "All files failed to upload"

S3 Endpoint: https://s3.us-west-004.backblazeb2.com
Region: I have tried a number of options, including us-west, us-west-004, us-west-004, and just leaving it blank
Access Key ID: 004xxxxxxxxxxxxxxxxxxxxx7
Secret Access Key: xxxx
Bucket: kalis-files
Public URL: https://cdn.dystopia.zip

The public URL is set up as a Fastly CDN with TLS, that should be set up correctly (even if it's wrong I don't see how it would effect uploading).

Any ideas? Have I missed something obvious? Thanks in advance- I know this probably isn't a typical thing you get asked as a Discord plugin dev lol.