Bucket name rules ("That isn't a valid bucket name")
A bucket name needs 3 to 63 lowercase letters, digits and hyphens, starting and ending with a letter or digit. Avoid periods, because they break secure (https) addresses. Your provider returned InvalidBucketName if Offloft shows "That isn't a valid bucket name." For example, my-site-media is fine.
Some setups add a rule. To serve Wasabi files through Cloudflare, or Akamai (Linode) files from your own domain, the bucket name must be that domain. This is the one case for periods. Decide before you create the bucket, because a name can't be changed.