Using HiveMQ as a MQTT Broker

I am using HiveMQ as a MQTT broker, which works as a dream from my WSP32 devices running Tasmota, but I have problems with the certificates when I try to set it up on Home Assistant.

I have tried to follow the brief information I found at How to Use HiveMQ Cloud MQTT Broker with Home Assistant
and fetced the isrgrootx1.pem, and set up my configuration file like this:
active: false
folder: mosquitto
mqtt:
broker: My HivewMQ Cluster
port: 8883
username: xxxxxx
password: xxxxxx
certificate: /root/cert/isrgrootx1.pem

Mqtt starts up, but I get an error in the logfile telling me that SSL is not enabled.

What can i do to fix this problem`?

I have just started testing Home Assistant (i have been using Node-Red so far) so I do not have deep knowledge.

Best regards

Ulf H.