Clog drain tube

[tsubaki]

If you haven't already removed the tube, shove the fishtape in as far as it will go, add a couple of feet, cut it off and connect to a battery drill motor.
You may have to rebend the end either smaller or larger either to "drill" thru or dislodge the obstruction.
Rebending is easy with a small propane torch. Everybody needs a short fishtape anyway, also.
There is the possibility the tube is pinched or kinked somewhere.