Did you try the [-f] option (see below)?
1.1 Tool Arguments and Usage
The synopsis for using the Repository Snapshot Manager tool is:
(operation) -backup or -restore =The operation you wish to perform.
p =The path to the base backup folder.
installer_location =Directory path on the server in which the Qlik Sense installer resides.
QlikSenseVersion =Qlik Sense product version (for example 2.0.1).
direct =Denotes whether an existing installation exists or not.
PathToSupportingContent =Directory path on the server in which additional artifacts used by the system reside.
c =The certificate password (if required/desired).
d =The database password (if required/desired).
usernameWithDomain =The user on the host with administrative privileges with the domain, for example “COMPANY_DOMAIN\USER”.
p =The password for the user associated with the domain.
f =The option to run the backup silent, for use with scheduled tasks.