Fresh install via packer not working

**Describe the bug**

Fresh seemingly successful install with packer, the commands show up but `:MarkdownPreview` command does nothing.

**To Reproduce**
Steps to reproduce the behavior:

1. Install with packer as per the instructions by placing the following into your `plugins.lua` file:

```
use({
"iamcco/markdown-preview.nvim",
run = function() vim.fn["mkdp#util#install"]() end,
})
```

2. Run `:PackerInstall` and note that `markdown-preview` has successfully installed
3. Open a `.md` file
4. Note that if you start to type the `:MarkdownPreview` command that you can tab complete it, ie this is showing that `markdown-preview` is indeed installed
5. Execute :MarkdownPreview and notice that nothing happens. No errors, and no preview opens in any browser.

**Expected behavior**

I expect that when I execute `:MarkdownPreview` that a preview should open in my browser.

**Desktop (please complete the following information):**

- OS: I've tried this on two machines, both running macOS 12.5. One of the machines has an M1 chip and the other is Intel. I'm also using kitty and tmux if that is relevant.