FATAL: Received: 403 Forbidden when creating cache on Digital ocean with private gitlab runner

I am running tests on digital ocean servers using gitlab runner. I want to cache gems so it won’t install gems from scratch for every build. The cache section in my gitlab-ci.yml looks like this:

[runners.cache]
    Type = "s3"
    ServerAddress = "ams3.digitaloceanspaces.com"
    AccessKey = "KEY"
    SecretKey = "SECRET"
    BucketName = "cache-for-builds"
    Insecure = true

When the build finishes and runner tries to create the cache I see

I tried to regenerate Digital Ocean Spaces key and secret but it didn’t help

Also I don’t have any certs installed on my private gitlab runner bastion server

The cache space in the Digital Ocean UI looks like this:

What I am doing wrong?
How can I debug this error?
How can I fix the Forbidden error?