First thing that comes to mind is... Are your engines on toggled "off" sidings and miss the watch dog signal.
You may have tooo much track on fixed 1 and fixed 2 resulting in a low dcs signal.
You may have a faulty tiu. (I3a comes to mind.)
Or and hopefully this is it..The track signal somehow got turned off. Turn it back on with
Menu/System/ DCS set up/ AON..the AON turns the dcs signal on to all channels
Good luck