What am I doing wrong?

I'm finally getting round to replacing CM with LOS on my OP3T.

I wanted to do a clean install so i backed up my files and downloaded the new TWRP, SU, GAPPS & LOS nightly....

I booted too recovery and flashed TWRP, no problem.

I thought the next step was to sideload the LOS Image but it's failing with an error 7 every time.

Any ideas.