I know there are several questions on SO about this, but none of them are helping to resolve my issue.
I want to be able to click a link from an email/text/browser>
Chrome does not open apps from manually-entered URI schemes. In fact, a manually-entered link will never launch an external app in Chrome. This is by design — for whatever reason, the Chrome team feels users should always be kept inside the browser after entering an address.
You can work around this to some extent by putting the deep link behind a user-drive action (a standard tag, for example), but the Chrome has its own standard called Chrome Intents that you are supposed to use instead. Depending on the device you are using, this could also be the case for the standard browser.
In other apps, it's up to the app in question whether a custom URI scheme is identified as a 'clickable link'. For best compatibility, you'll want to wrap it inside a regular http:// link with a redirect.
If you're interested in an in-depth explanation of the complications around deep linking, this post is a good place to start. If you just want it to work without a lot of extra effort, Branch.io (full disclosure: I'm on the Branch team) solves this problem as a free service.