Make sure the file app/etc/hyva-themes.json is including the path vendor/loki-checkout/magento2-core (and possibly other modules that you have added). When in doubt, run:
bin/magento hyva:config:generate
Rebuild your Tailwind classes (in this case assuming that Yireo/example is your own theme);
cd app/design/frontend/Yireo/example/web/tailwind/
npm run build
npm run watch
Make sure to refresh the page with Browser Cache disabled