WebView + Grafana = empty iframe

Hi,
two days of hard migration and now I’m having just one problem left.
I’ve one server for influxdb and one oh2. Inside influxdb server there is grafana on top installed. Via direkt link I am able to see my graph. Inside OH2 I set up several static html files. These files are called inside my sitemap vie Webview. The created iframes are empty.

Sitemap
Webview url=“http://172.31.XXX.XXX:8080/static/EnergyHour.html” height=15 visibility=[En_Chart_Period==“0”]

/etc/openhab2/html/EnergyHour.html

All trailing brackets are removed…
!DOCTYPE html>
html>
head>
meta http-equiv=“Content-type” CONTENT=“text/html; charset=utf-8”>
link rel=“stylesheet” type=“text/css” href=“http://172.31.200.116:8080/static/charts.css”/>
/head>

div class="container">
    <iframe src="http://172.31.200.181:3000/dashboard-solo/db/openhab?from=now-1h&to=now&orgId=1&panelId=1&theme=light" width="100%" height="400px"></iframe>
/div>

/br>
/html>

Anybody any ideas? Thanks in advance.

It is working on Chromium… so I think Firefox is my problem.