I've made edits to my Coming Soon page and clicked 'Activate', but it's not showing my changes when I view it online.

Usually, if Shopify’s “password protected” feature is enabled (which it is by default on new stores), it prevents your custom changes from showing.

1. Navigate to your store’s dashboard (your-website.com/admin).
2. Go into Online Store > Preferences.
3. Scroll down to the Password protection section.
4. Disable password protection by unchecking the box next to Enable password.