Hello,
I use Zeus icons on my HA Lovelace.
When I’m on the Web interface in my computer, it’s OK. But when i go to the mobil App ( android and IOS ) the icons doesn’t display. If I reload core HA with service, or if i change statut of sensor, the icon appears.
I can confirm inconsistent behaviour. Self-made icons are shown in a browser but not in android app:
check that android system webview is up to date, you can also try to get the debug logs and see if any errors are showing up. There are 2 types of logs here, one of which is ADB logcat and the other is chrome developer tools to get the actual webview errors which is what this is. More than likely the self made icons need an update to support better caching to work with android webview.
I’m running Android 11 on a Samsung S20 with all the latest updates. My Android System WebView is the latest version 87.0.4280.101 from 07.12.2020.
The solution was simple: go into Android settings for the HA app and clear the cache there.
You will probably hit the issue again in the future 
if your using a custom component id suggest reaching out so they can fix the issue
