composer.json requires {pluginname}, it could not be found in any version, there may

I'm trying to create a private repo on my own github account to store some paid plugins and then require them into a roots bedrock website, but I keep getting the following message for eacch of the plugins:

composer.json requires {pluginname}, it could not be found in any version, there may be a typo in the package name

I'm using the following repo setting:

Code:

---

"repositories": [
  ...
  {
        "type":"vcs",
        "url":"https://github.com/{mygithubacct}/{reponame}"
  },
  ...
]

---

and then the following require:

Code:

---

"require": {
  ...
  "{pluginname}": "^3.1",
  ...
}

---

The repo definitely contains the plugin and pluginname is the same name as in the plugin's composer.json.

I've created a deploy key, which definitely works, as I was getting a conneection problem, until I created it and put it into auth.json, which looks like this:

Code:

---

{
  "github-oauth": {
        "github.com": "{token}"
  }
}

---

The only thing I can think of is that my repo is not in the correct format. It currently contains the unzipped plugins in their own folder i.e. copied directly from the Wordpress plugins folder.

Is that correct or should they be zip files?

If that is correct, what else could be causing the not found message?

I've also seen the following meesage appearing above the error message:

Code:

---

Info from https://repo.packagist.org:

---

Does that mean that composer is ignoring my repo and looking directly in packagist? If so, how can I get it to actually use my repo?