The CTI link uses the IPO system password to communicate between the ACCS server and the IPO. Double-check it (ACCS Server Configuration/network settings, IPO security settings/system password), and also check port 50797 is open between the ACCS and the IPO server (firewall)
For the Workplace URL, Chrome or any browser will cover/convert the space with some characters, which in this case is %20, so that was causing this issue.
http://<WorkspacesIP>:31380/Login/?returnpage=../services/UnifiedAgentControll%20er/workspaces/
but the correct URL is http://<WorkspacesIP>:31380/Login/?returnpage=../services/UnifiedAgentController/workspaces/
Removing the space character and relaunching the page fixed the issue and the Workspaces page launched fine and the Agent was able to log in.