Cant access Mosquitto MQTT broker from client on local network

I have a 20.04 server installed with Mosquitto MQTT broker. It works fine when using the server on the local localhost

mosquitto_pub -t 'test/topic' -m 'helloWorld

However trying to use "MQTT Explorer" on a windows-machine on the same local network fails. The client just shows "Disconnected from Server". (I have tried ti use the MQTT broker on another server (Home Assistant) and there the MWTT Explorer client works fine)

When starting mosquitto in verbose mode "-v" I see traces when using local host client but nothing from the windows client. Putty works from the windows server on same IP address. I just can figure out how to troubleshoot this issue, input greatly appreciated..

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