How can I resolve the error "Access denied" or "The username and password are incorrect while running a robocopy script?

While running a simple robocopy script to make a back up of a folder from the server where PRTG core is installed, this error message appeared: ERROR 1326 (0x0000052E) Creating Destination Directory NASAddress\RMBACKUP\ The user name or password is incorrect

You need to enter credentials of an administrator for the target device to execute the script out of PRTG.

Disclaimer:
The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.