This could be if you are using lab, as i am also facing the same in the lab. i am relaunching the lab , it's working for me. ypu may try the sameguys I am facing one issue, after filling a complete cell with comments and after using another cell for excution..i am unable to excute..I mean all the cells are star marked .
Can anyone help
if you are facing problem then please try first uninstall this and then reinstall it.
somewhere on your file you declared either np or array as variable... try to write this in new file it will work.