App works on desktop but not on mobile

We added an app to our own organization. It works on the desktop client but not on the mobile client.
I see the app but when I open it, it just stays black.
We use the loginHint in the contentUrl.

We use the following config for the staticTabs:
"staticTabs": [
{
"entityId": "de.someid.startTab",
"name": "App Name",
"contentUrl": "https://server/appname/app/teams?uid={loginHint}",
"scopes": [
"personal"
]
}