Issue comes where HC panel logout or session breakup after the new domain creation. To resolve this issue follow the instructions below.
Login in HC Panel as host admin and go to My Server :: Configure Panel :: General Setting. Two options would be listing:
For option 1 (admin.domain.com):
Open IIS :: Application Pool :: HCAppPool :: properties :: Chose Mode = Classic Mode.
Recycle the HCAppPool.
For option 2 (domain.com/admin):
Option 1 workaround does not work with domain.com/admin. To make it workable on IIS 7, set readonly attributes in the web.config file located under the path C:\Program Files\Advanced Communications\HostingController\Web\web.config on web server machine.
Trouble logging in? Simply enter your email address OR username in order to reset your password.
For faster and more reliable delivery, add email@example.com to your trusted senders list in your email software.