What's at the other end of those three flight lines in
the first image? Looks like the error purports that one
of those connections is not made.
Might use a DRC run to check for gaps you can't see
in routes you think are completed. Might use an
extracted view (I do not use ADS but presume there
has to be that intermediate database between the
original drawn layout and netlist) and try selecting
the trouble net, looking for "broken branches".