Chosen Solution
. I have purchase used ssd on your website that compatibles with my Mac model. Then I started rebooting and MacOS processed nearly 80% then prohibited symbol appears. How to resolve this problem?
It’s very likely that the drive you purchased has installed an older Mac Os version than your Mac is allowed to run with, which is the latest that was available at your Mac manufacturing date. Flash drives running on your model were on the market already two years before your Air was manufactured. You will need an install Usb stick with High Sierra (Sierra would probably work too), start your Mac with option key pressed to select the installer. Or you could install over the internet if you prefer..that will install latest available version of Mojave..press option+R at system boot in this case.
