I am not sure if you fixed your problem yet but I just ran into a similar problem but in case you didn’t or someone else is having the same problem, I wanted to post what worked for me.
Here are a few things to check that helped me.
1. Make sure TeX it is enabled (eye is open) under administrator --> modules --> Filters --> manage filters
2. Look at the TeX Notation link also under filters. If you have a Red X next to the latex and dvips binaries then your path is incorrect or you don’t have latex installed. I used yum to install latex
yum install tetex-latex
someone also suggested this: yum install latex
Now if you also have a red X next to convert binary your path is incorrect or you need to install gostscript or ImageMagic I installed ImageMagic and if fixed the problem.
yum install imagemagic
If you are using apt-get then just do a google search to find how to install those. I hope this helps. I am new to Moodle and this is how I fixed my problem so I hope it will help someone else.