While initializing the remote control session, an error message occurs stating:
Unable to establish a remote control session:
Your username and password were valid but you were not recognized by the Remote Control Management Server as a registered user of this host.
Ensure that the user name that you are trying to connect as has been granted permission on the management server.
Why am I unable to take the Remote Control of a machine though the user name and password are validated ?
The error message clearly shows that it's not a credentials issue but a configuration issue.*
Check the RC Status of the machine in question in the DSM Explorer\Computers and Users\All Computers\<Machine>.
If it shows as "Listening (Local Security)", make the following changes to the policy applied to the machine(s):
Go to Control Panel\Configuration\Configuration Policy\Default Computer Policy\DSM\Remote Control\Host\Managed
Change the Centralized Security to True
If the machine shows as just "Listening", check the effective settings for the machine. This can be done by right clicking on the machine in the DSM explorer, going to Remote Control then effective settings. Enter or select the user or group you are attempting to connect with and hit add to list and ok. This will then show you what permissions that user has for that machine.
If the user is not allowed to perform the connection type being attempted, the following message will show up.
In this case grant the user permissions. This can be handled under the group that the computer is located in, under [Group Details]> Remote Control Permissions.
If they are allowed to perform the connection type but it is still getting rejected, please open an issue with support.
*NOTE: Please also check that permissions are set not just in Security Profiles, but also in the Remote Control 'Address Book' which can be found under any group, including the 'ALL COMPUTERS' group to define who may use Remote Control for computers that are members of that group. To find the address book, just expand the group, like 'All Computers', then expand '{group details}' and find the item called 'Remote Control Permissions'. When you click on this, the defined users and groups will be displayed on the right side of the display. To add user(s) or group(s), just right click on 'Remote Control Permissions' and select 'Add User'.