Enable CORS on custom domain Cloud storage bucket

I've set up a Google Cloud Storage bucket with the name of my custom domain (media.xxxxx.tech). This way I can point the nameservers with a CNAME record to c.storage.googleapis.com and access the files at media.xxxxx.tech/[file path]. I've just followed this guide on how to enable cors. Even after waiting a couple of hours, nothing changed and there are not Access allow origin headers present. This is my cors config:

[
  {
    "origin": ["content.*****.tech"],
    "method": ["GET"],
    "responseHeader": [],
    "maxAgeSeconds": 3600
  }
]

What do I do wrong? How can I solve the problem? Thanks in Advance!