Largish field.

Whatīs your controller hw ?
Smoothstepper ESS, Pokeys, CSLabs CSMIO, PP, something else ?
Does it have a plugin installed into mach3 correctly ?

Look at diags / plugins.
Your controller shuld be visible, if it is installed.

Are your using flash screens ?
Itīs a tickbox on the settings (last) page.

First guess is that your plugin is not installed.
Take pics of your hw box and we can say what you have.
Take pics of your setup screens and we can guide you.