A design has five carry-in logic blocks in each column and passes the carryin signal from the fifth block of first column to the first block of second column.
This design had been working in PlanAhead previously.
However, when migrated to Vivado, route_design reports a critical warning
The route status shows "routable but not routed".
This design has an XDC macro that forces a broken carry chain (COUT-->CIN not aligned) and so CYINIT needs to be routed using an AX route-thru.
Because there is also an active signal on DI0, that signal needs to be routed with an A5LUT route-thru so as to reserve AX for the CYINIT.
None of this is happening (even if CYINIT is routed alone) and so the CYINIT connection ends up unrouted.