Starting with HXDP 2.5 and later releases, we have a new HX Connect UI. To login as a local administrator, try "local/root" and use the user-supplied controller VM password you specified during installation.
You also have the option to login using vCenter SSO. As an example, you can sign in using email@example.com. User privileges in HX Connect UI are based on assigned vCenter roles. Make sure time is properly synced on vCenter and your HX cluster for this SSO auth functionality to work properly.
Please give these options a try.