How can I send a private extension made for my friends only?

So I have an addon that is made for a website that we don’t want the public knowing the domain to. When uploading my extension, I selected the private version but now if I send them the https://addons.mozilla.org/en-GB/firefox/addon/extName/ url, it says

Oops! We can’t find that page

https://extensionworkshop.com/documentation/publish/signing-and-distribution-overview/#distributing-your-addon