Target path for OS failed

Hello

i have a ES station which contain step 7 manager and wincc scada V7.5 configuration , and i have two single stations as operators stations which have only WINCC SCADA RT 

the ES station and the two single stations are connected to each other via ETHERNET local network 

the ES stationcontains the two WINCC SCADA projects for the two stations (which are integrated in STEP7 manager) 

my need is to download directly the WINCC projects from ES station into operator stations , i set the path of the target computer (for each station) in the property of WINCC project inside STEP7 (OS cible et OS standby Tab) as it is described in attached file 

but i can't do that , i got a message error "invalid target path" , how can i solve this problem?

thank you in advance