So we have discovered that the SDM_Login operator is a custom operator that perhaps comes with Service Catalog? Not sure about its origin, but the point is that it is not controlled by the settings on the Configuration tab for the CA ServiceDesk connector.
If you open the properties for the SDM_Login operator, on the Connection tab there is a dataset field:
This dataset is what this custom operator uses to build the Service Desk web service URL. In the code of the operator it looks like this:
"http://" + Datasets[M_PATH__].server + ":" + Datasets[M_PATH__].port + "/axis/services/USD_R11_WebService"
So it is substituting the server and port with the values from whatever dataset you are giving it here. And since you are getting an error that ServiceDesk is not available, it must be pulling invalid values from the dataset. So you will need to check this dataset and make sure the ServiceDesk information is correct.
Hopefully that will get this working for you.