I can’t figure out if this is because Firefox is stopping it because it is http not https and gives a warning about not being secure, or if there is something else I should be doing.
I added the following to my config.
// Click tracking
// If you set this to 1, all links in your emails will be converted to links that
// go via phpList. This will make sure that clicks are tracked. Default: 1
// If you disable a URL conversion, set to 0.
define('CLICKTRACK', 1);