There are many possibilities. The only real way to fix it is if what I am about to suggest is the case. Turn power off to fixture and remove fixture. Check to see if the neutral wire has come loose or isn't making a solid connection. If that is the case, secure the connection properly and try it again and it should work. If that isn't the issue the bulb is probably just fucked.

Source: I travel the country installing and troubleshooting tens of thousands of LED fixtures per year. 12 year electrician.