I can see the symbols with not errors reported.
Here is my own test
math]P_{i} = \frac{e^{-\beta E_{i}}}{Z}[/tex]
[LaTeX ERROR: Convert failed]
tex]P_{i} = \frac{e^{-\beta E_{i}}}{Z}[/tex]
It would seem this forum accepts "tex][/tex]" tabs but not mathml tabs "math][/tex]"
Note I have left off the leading [ to make the tabs visible.