Can't seem to register a new Page Template

Hello, again ??
So I’m trying to build an Archive page, and the first step – I figured – was to create a template for it, so I could apply Archive-specific sidebars, etc. However, when I create the new template (with the Template Name and all that in the PHP comment) and upload it, it never shows up in my available page templates. Am I doing something wrong for a Customizr Child Theme? Is there a different way to handle that within this setting?

Thanks so much for your help!

Best wishes,

Tom.