When a tlc plate was developed the solvent front ran off the top of the plate, why?

Question

A two component mixture containing a dicarboxylic acid and tricarboxylic acid gave only one spot with an Rf value of 0.05. Solvent used; hexane. What went wrong?

Solvent runs off the top because the plate was developed too long.

The carboxylic acids were not separated because the solid (the immovable phase) attracted the two acids equally )or too much) and/or the acids were equally soluble in hexane.