Can Face ID be repaired

You yourself changed the screen or you paid someone other than Apple or an actual Apple Authorized Service Provider to change the screen? If anyone other than Apple of AASP replaced the screen, then you don't have an authentic Apple screen on your iPhone. And that means Face ID is now permanently disabled and the ONLY way you get it back is to see IF Apple would be willing to replace the unauthentic screen on your iPhone. Which they may refuse to do as they typically will not touch an iPhone which has been tampered with by anyone other than them or an AASP.

If the screen was not changed by Apple or an Apple authorized service center, then it is most likely that your Face ID will never work.