I developed the extension and that extension is displayed on Checkout page. But it is hidden sometimes. Is here anyone who is experienced on this?

I've made a couple of simple extensions in SuiteCommerce Standard to inject client-side browser javascript and style tags into the pages, but then found the SMT to work much better for that purpose. So I have very little experience implementing Extensions in the way they're meant to be used, but tell me more; maybe I can get an idea of how to fix it anyway.