Hi
I'm afraid I'm totally stuck.
THe download comes as a .tar not a .zip. so This isn't recognised for local update within the phone.
So, trying to use the flashtool, again, the TAZ file, not a zip, which I can extract using winzip, but the resulting folder does no contain a suitable target file for the Scatter Loading .

I will try to reproduce that.
Which file are you trying to flash?

for version BV7000_Blackview_20170412-2 you find the scatter file at t728y-jk-bv7000-63-fhd-128g16g-bom13-N_BV7000_Blackview_20170412-sign_user/MT6737T_Android_scatter.txt

if that not work try to use an newer version of flash tool