Here's the synopsis:

Jack Malik is a struggling singer-songwriter in an English seaside town whose dreams of fame are rapidly fading, despite the fierce devotion and support of his childhood best friend, Ellie. After a freak bus accident during a mysterious global blackout, Jack wakes up to discover that The Beatles have never existed. Performing songs by the greatest band in history to a world that has never heard them, Jack becomes on overnight sensation with a little help from his agent.

https://www.youtube.com/watch?v=6uqvgPm8U4c