Norton 360 not holding definition updates

Yesterday, my desktop with Norton 360 wouldn't finishing loading updated definitions of 256 MB despite being left on

all night to complete the task.  Tried running Norton Power Eraser and downloaded update for  that yesterday, but still get the message I need newer version.  Should I reinstall Norton 360, run Malewarebytes?  It's frustrating, I should be working.

       Thanks, Theresa