No start up disk

I recently decided that I wasn’t Ed to restart (clear) my Mac book air 2019. At first I managed to get to MacOS utilities go on disk utilities and erase Macintosh HD (I also applied first aid to all volumes etc) then reinstall macOS Mojave. However after it finished installing it came up with a spinning globe, I type in my internet pass words and then it instantly takes me to macOS utilities again with a pop up mentioning that I do not have a startup disk. I then go to chose a start up disk but there is nothing there. I have repeated the steps of erasing disk applying first air and then installing max OS (with the help of apple support and their senior team) all together I’ve now done this 7 times and nothing seems to help it always take me to the spinning globe then staring back to the pop up of needing to select a start disk but non are there to select. Apple support think I should take it in to get looked at which is fine but want to check if anyone else as experienced the same and if so what did they have to do?

thanks