Snips on Mac only works at work



Hi there,
I have installed Snips at my Raspberry PI and later also on my Mac computer. I now have the strange bug that Snips on Mac online works when I’m at work - with a different wifi. At home, Snips on Mac don’t work, the Node.JS app can’t connect to the MQTT broker.
At home I have installed first SAM on my Raspberry and later Snips for Mac OS. On my Mac I have the following software installed:
Node 8.11.1
NPM 6.4.1
macOS Mojave 10.14.2

Can somebody give me a hint in which direction I have to search? I think that maybe the SAM installation on my Raspberry is making problems with the Snips installation on the Mac? Or maybe my wifi home router blocks MQTT connections and at work the port is open?

Thanks in advanced,