Like yvmuell said, you could try the web-installer again from the beginning. If this does not work then I would suggest to reinstall FPOS and then try to flash e/os manually following this guide
I did it recently with with a windows laptop and it went pretty smoothly. It took an hour or so with all the rebooting of the phone and going through the initial setup every time, though I think if you don’t setup anything it will go faster.