server_name variable in HTML title are not replaced

[mvanbaak]

Template

Plex Guide

What happened?

When I build the mkdoc (or serve it) it shows the following in the HTML title:
<title>{{ server_name }} Streaming - MvBPlex Server Guide</title>

Expected behavior

HTML title tag like this: <title>MvBPlex Streaming - MvBPlex Server Guide</title>

Steps to reproduce

No response

Configuration

MkDocs version

No response