How can I fix unresponsive Face ID on iPhone?

Unfortunately, that is usually a hardware problem, but this Apple support guidance has some suggestions→If Face ID is disabled on your iPhone or iPad Pro - Apple Support. Note that the last suggestion is a link to contact Apple Support to discuss hardware repair options.

tope67 wrote:

My Face ID suddenly stop and I want to use it

[Re-Titled by Moderator]

Try the suggestions in this link --> If Face ID isn't working on your iPhone or iPad Pro - Apple Support