There are media reports currently circulating about Apple iPhone 8 screens that have been repaired by an unofficial third party. The issue is reported to prevent the screen from working after updating to iOS 11.3.
Apple have not directly commented on this issue yet.
However after the release of a previous iOS version Apple said “non-genuine replacement displays may have compromised visual quality and may fail to work correctly. Apple-certified screen repairs are performed by trusted experts who use genuine Apple parts.”
Please keep an eye on the news feed for any further updates on this issue.