bpbrm error - Cannot execute cmd on client

Could be lots of things. A very good check is with bpclntcmd, using the -self, -server <master server> options from both client and master server. You will usually find that one of the options in a particular direction does not resolve. Also check hosts file (and if you have DNS temporarily rename the hosts file on the Master server to run a quick test backup)

E:\Program Files\VERITAS\NetBackup\bin>bpclntcmd -?
bpclntcmd: unrecognized option -?
bpclntcmd: -sv
bpclntcmd: -pn
bpclntcmd: -self
bpclntcmd: -hn <hostname>
bpclntcmd: -server <NBU master>
bpclntcmd: -ip <ipaddress>
bpclntcmd: -gethostname
bpclntcmd: -is_local_host <hostname>
bpclntcmd: -check_vxss
bpclntcmd: -check_vxss_with_host <hostname>
bpclntcmd: -get_pbx_port [<hostname>]
bpclntcmd: -get_remote_host_version <hostname>
bpclntcmd: -get_local_client_patch_version
bpclntcmd: -get_local_server_patch_version
bpclntcmd: -sanclient <0|1>