It violates the Heisenberg Uncertainty Principle. The Bohr atomic model theory considers electrons to have both a known radius and orbit i.e. known position and momentum at the same time, which is impossible according to Heisenberg.
The Bohr atomic model theory made correct predictions for smaller sized atoms like hydrogen, but poor spectral predictions are obtained when larger atoms are considered.
It failed to explain the Zeeman effect when the spectral line is split into several components in the presence of a magnetic field.
It failed to explain the Stark effect when the spectral line gets split up into fine lines in the presence of an electric field.