Hi there, @darrenjlobb. Welcome to the forum!
You’re correct in assuming SSL is required. I’m a little concerned though if you’re getting warnings about https in the browser. Chrome doesn’t usually do that unless there’s something it doesn’t like about the certificate. Is it a self-signed certificate by any chance?
Also, I would probably recommend running the mobile as from the PWA website, instead of the Play Store APK. We’re not updating it as frequently b/c of general issues with native releases, but it’s the same app, and can even be “installed” to your home screen. More details here:
Let me know if you’re still having trouble, hope this helps!