Clueless why - tasmota mqtt connection refused rc5


i´m trying to get my fist mqtt devices into HA, i´ve got mosqouito mqtt broker and tasmota integration.
I have set up the mqtt broker with user and pw and the first device, a nous A1T socket is connected without any problems.
My second device is called bitshake smartmeterreader also with tasmota and despite having 1:1 the same setting I only get
19:36:33.947 MQT: Verbindungsversuch…
19:36:33.949 MQT: Authenticating with an Azure IoT Hub Token
19:36:34.377 MQT: Verbindung fehlgeschlagen aufgrund von, rc 5. Wiederversuch in 120 s"

meaning connection refused, rc 5 which should mean wrong credentials.
Both devices share the same wifi network and I can log into both per http just fine.
HA is running on synology vm
-because of the sml i´m advised not to update the firmware on the bitshake device.

  • i´ve enabled debug logging but don´t see any entries of failed logins
    -i´ve played around with the username and length of the pw but no effect.

this one is refusing to connect:

this is running just fine:

can anybody guess what i am missing here?