This appears to running as a Multicast, and we cannot find a subnet rep. In LDMS 9.5 and older we use a Subnet Directed Broadcast (SDB) to locate a machine to act as the Multicast Domain Rep (Also known as an MDR or Subnet Rep). However networks are not always configured to allow a SDB to route. So the solution is to specify manually which machine you would like to act as an MDR by adding them to Network View - Corename - Configuration - Multicast Domain Representatives in the console. From there the Core will always try those machines directly and then only try the SDB. As long as one of the machines in that group are available they should be elected as MDR, even if they are not part of the task itself.
In LDMS 9.6 the clients in the task always organized amongst themselves who will act as the MDR and the core does not have to try sending out SDBs that will get dropped by the router. Which is far more reliable as all the multicast traffic stays local to the subnet where it is unlikely to be interfered with.
Otherwise in the mean time you can switch from a method using Multicast, to a regular download of the files. If you need to be considerate of bandwidth on WAN connections to remote offices the best option is to employ the use of Preferred Servers.