The "math" module is still mostly borked - it relies on an external site to do some of the work and that seems to be not working most of the time now.
Historically its been a massive PITA to get everything needed for math rendering installed all on site - hence the reliance on the external site - however that is supposed to be changing with the next version of MediaWiki (released next month). So with a bit of luck it should be fixed and working better than before shortly.