The Yahoo IT technicians - who probably don't have any certifications or real world experience don't know if this is a hardware or software problem. They don't have a clue if this is a physical layer or application layer problem.
Maybe the cabinet that stores the servers for the TNA, TZA, FAZ, FAS, QQQ, VXX and EPHE boards lost its power.
Maybe the janitor that cleans and vacuum forgot to put back the cabinet's power cord in the outlet they used.
Yahoo employees aren't being allowed to work from home anymore, which is 100% idiotic so they are protesting by messing up some stuff here and there.
Work from home allows - less use of foreign oil, less traffic for those who just can't do it, less gas money spent so more money for other stuff, less accidents, less pollution, less road rage. Demand your company allow it as often as is possible!
They are inaccessible with a warning message of "MBHo_BOARD_NOT_FOUND". (do a search for the MB).. so they are either inaccessible and deleted or inaccessible. That's all we know. Yahoo is a very transparent company that way.