Hello -
There could be a few things causing this. Do you have a firewall? If so, are all the ports open? Below is a link to the default ports.
https://docops.ca.com/display/DTS85/Default+Port+Numbers
Are you using IP Address or machine name? Can your machine resolve the machine name of the server?
Did you make sure Registry is up and running?
If you are still having these issues after my suggestions, you can open a support case. A webex might be helpful with this.
Hope this helps.
Thank you -
Stephanie