ArduinoIoTCloudTCP::handle_ConnectMqttBroker could not connect to mqtts-up.iot.arduino.cc:8884
Same problem here on an UNO R4 WiFi. It was working a month ago. I am now coming back to retry it after it has not been used online for 3 weeks. Rebooted the router, restarted the computer, reloaded the software via the (new) online editor, now stuck with this report on the serial monitor and the device shows offline on Arduino Cloud. Same report with serial monitor via IDE 2.3.0.
I found the problem to be that the Secret_Key was different in the sketch file (secret tab on the online editor) vs. the Network Panel on the Setup tab for the "thing" my device was attached to.
(Also of note for similar problem getting online is that the Password for my wifi network is now called 'SECRET_OPTIONAL_PASS' instead of 'SECRET_PASS'. which had to be changed in the sketch itself.)