No , it doesnt means that it is fixed that you will not get seat in any of the NIT, mock allotment just gives the idea according to the ranks, you should wait and try you may get seat , mock means tentative it depends on the need of hour that you will get seat in NIT

hello kruty

getting no seat in mock allocation does not mean you will not get a seat till round 7 as you must have filled your choices based on last round cutoff.

however to be on the safer side you must fill some choices which you are definitely getting it

all the best