@hpeters I meant to respond to this ages ago, just life has been a bit hectic 😅
The iPhone 13 Front facing camera and Face ID is a complex mesh of components. It sounds like this shop has replaced the True Depth camera assembly and the receiver speaker.
I’m unclear as to whether or not they replaced the sensor cable on the display. But that’s what I’m referencing. It’s just that there are no cameras or speakers attached to that cable on the back of the display, but there are still sensors on a cable that lives around the camera cutouts in the screen.
That’s most likely your issue. They could even have replaced it, but the cable they put in is faulty.