Windows defender is probably on your local pc, not the server. There should be a fix it/try to repair option in the bottom right.
Have you also rebooted your desktop? If not do that first please and try the dashboard again.
If it still does not open you can remote to the server desktop and open it from there.
Start >run>MSTSC>enter
computername is whatever wdsentinel MY server whatever
username is administrator
password for the administrator account
