My phone currently has the latest update and I am still unable to use face detection , what is the next step?

If you just have issues with Face ID not working properly, read this document:

'If Face ID isn't working on your iPhone or iPad Pro', click here --> https://support.apple.com/HT208114

If you see a 'Face ID disabled' message, this document deals with that specific issue:

"If an alert says Face ID has been disabled on your iPhone or iPad Pro", click here --> https://support.apple.com/HT208186

Make an appointment at the Genius Bar and have it checked. it's most likely a hardware fault.