I would navigate to the directory C:\Program Files\SASHome view the sassw.config file. You will see an entry in there that should point to the server configuration file. It will look something like this:
SASENVIRONMENTSURL=http://xxxxxx.demo.sas.com:80/sas/sas-environment.xml
where "xxxxxx.demo.sas.com" is the URL of your mid-tier server. Copy the HTML address from this statement and place it in a Web Browser on the same client machine and see if you get a well formed XML document open up.
If not, confirm that this is the proper address of your mid-tier server.
Once this address properly resolves or points to the correct sas-environment.xml file, you should be able to log in.