See my comment after step 28 if you are running High Sierra and have converted your SSD to the new filesystem.

Be careful if you are running High Sierra and have converted your SSD to the new file system. I replaced my logic board after updating to High Sierra and converting my SSD. The new board would not recognize the drive. I restored the system from a Sierra backup image and all is fine. My assumption is that the High SIerra update includes firmware changes to support the new file system.