How to fix Face ID issues after repair on iPhone X?

Repairs from an Apple Store or Apple Authorized Service Provider have a 90 day warranty to cover defects in replacement parts or workmanship. If that is the case, return to them. If you had your iPhone repaired at a third-party service provider, there's no telling in what they do. They do not have access to genuine Apple parts nor manuals/trained technicians. As a result, any warranty will have been voided and service options from Apple.

If the work was done by someone other than apple or an authorized service provide, no. Face ID will never work on that device again and Apple won't touch it since it's been tampered with.

If you have taken a service from a third-party service provider go back to them and seek their opinion.