It won't wash!

not wash

To not be accepted or believed. That kind of excuse may have worked in high school, but it doesn't wash with me. The deadline for the paper is tomorrow, no extensions. He may be able to skirt the issue in some regions, but that approach won't wash in these parts—these people want straight answers.
See also: not, wash
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

It won't wash!

Fig. Nobody will believe it! Sorry, it won't wash. Try another approach. Don't expect me to believe that! It won't wash.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
See also:
Full browser ?