Can only access machines on my LAN network, others time out on Connection

Have been using TV for some time for a network of remote machines.  Upgraded to v15 on all last year and worked A1, but now I can only access the 1 machine that's on my local LAN network.  The others all show as online, with correct settings and passwords saved, but simply time out when connecting.  

This happens whether I use TV on my PC or my Mac, and whether I'm connected to my local WiFi or via my mobile phone hotspot.