We are also facing this problem with TRB255 (TRB2_R_00.07.01.4)
The limit in the input field "connection string" is 150, but there is absolute no error or warning.
If copy paste the connection string it look like everyting is OK, but if you then go to CLI and run azure_iothub you see this error :
Error: Time:Tue May 3 21:07:22 2022 File:azure_iothub-89127a34c09401562924edac77abb54030323484-2021-06-22/src/c-utility/src/base64.c Func:Base64_Decoder Line:201 Invalid length Base64 string!
Error: Time:Tue May 3 21:07:22 2022 File:azure_iothub-89127a34c09401562924edac77abb54030323484-2021-06-22/src/c-utility/src/sastoken.c Func:construct_sas_token Line:217 Unable to decode the key for generating the SAS.
Error: Time:Tue May 3 21:07:22
2022 File:azure_iothub-89127a34c09401562924edac77abb54030323484-2021-06-22/src/iothub_client/src/iothub_client_authorization.c Func:IoTHubClient_Auth_Get_SasToken Line:411 Failed creating sas_token
Error: Time:Tue May 3 21:07:22 2022 File:azure_iothub-89127a34c09401562924edac77abb54030323484-2021-06-22/src/iothub_client/src/iothubtransport_mqtt_common.c Func:SendMqttConnectMsg Line:2029 failure getting sas token from IoTHubClient_Auth_Get_SasToken.
If you then deepdive into the source code (it is on microsoft gitbhub) you see that "sharedacceskey" value (last of the string that is cut off) must be MOD 4 dividable, which it is not.
We are using Azure IOT Central (which uses IOT Hub in the background) so we adjusted the DeviceId name so that the total connection string lenght is below 150. But I think the 150 is just some "number" that ever has been put in and should be increased in the next firmware update (+ a warning message if above the limit)
I also "data to server" has to bug because there we also are not able to make a connection to Azure IOT