Drawing object not display.

Hi,

Previously i'm using autocad LT 2012 and i save the file in 2000 version (.dwg).

after i upgrade to autocad LT 2016, i open the same file which i save in 2000 version seems that there are some missing object.

and i use the autocad LT 2012 to open the same file again, the object was shown.

may i know why? and how to show all the object in autocad LT 2016?

Please advise.

Thanks.