Montano, 32, (4-3-0), was supposed to face Wu Yanan last Saturday, which would have been her first bout since losing to Julianna Pena in July 2019.
But she tipped the scales at 143 pounds, seven pounds over the 136 pound limit.
Montana tried to explain what happened in an Instagram post, but it’s clear the UFC was not convinced.
Montano gained popularity during her run on TUF 26, winning the inaugural flyweight belt by defeating Roxanne Modafferi.
But eight of Montano’s last 10 scheduled bouts ended up being cancelled. Even a move up to bantamweight from flyweight could not solve the problem.
Montano was scratched from three previous contests coming into UFC on ESPN 28. USADA also handed her a six-month suspension for the drug Ostarine in November 2018.
Montano has not yet officially confirmed her release.