Test of Latex rendering

It is kind of odd.

$\LaTeX$ is working. For instance if I type this:

$H_a: \theta>\theta_0$

I get this: $H_a: \theta>\theta_0$

$/not$

Now, the \neq or \not do not render properly. I see the equal with a superimposed square symbol, as if the font would not exist.

$\mu \neq \mu_0$

$\mu \not \mu_0$