Gstr 1e || table 6a of form gstr1 || gst

i have to file gstr 1e || Table 6A of FORM GSTR1 || for the m/o Aug 2017 

but 

it shows the error that previous period return not filed (clarify that which return it is talking about??)

and gstr 1 for JULY and gstr3b for JULY and AUG were already filed . . .