Ok, I know this is strange but for YEARS, I have used my pinky as Touch ID on my iPhone SE (original) and , more recently2022 MBP.
Now, even if I set up the pinky, it does not unlock the phone.
And now I am seeing more signed that the finger next to my pinky is also not reliably unlocking my phone nor my MBP.
If this is just me, OK, but I really would like to learn if there might be a systemic issue.
Thank for reading
Nothing lately but I did have an issue a few years back when I was doing some major renovations to my house. My hands and fingers got so rough that the fingerprint sensors would no longer recognize them. Reprogrammed them and it fixed the issue. The only TouchID device I currently have is the keyboard on my iMac and it works well.
I have found over the years (iPhone, iPad, Magic Keyboard) that my fingerprints work for some variable period of time and then don’t. Short as a month, or long as 18 months. No clue as to why they stop.
Deleting them in System Settings and adding them back in works to get them working again.
Our friend @geoffduncan, who plays bass and guitar professionally, says that lots of musicians can’t use Touch ID or even touchscreens effectively because of their calluses.
My wife is unable to use TouchID on her iPhone and iPad. I am able to use TouchID on those same devices. We have deleted her fingerprints and re-entered them several times–same result. So she opens her devices by typing in her passcode. Something about her fingers and Touch ID is not compatible.
I’ve never been able to get Touch ID to recognize my fingerprints, even right after programming it initially for my use. And same as your friend, I have a hard time getting touchscreens to recognize my swiping or touch. I’m not a musician, but my hands are always callused. I’m betting this is a lot more common than is generally known.
Same here. Never as short as a month, but I absolutely have to go in at least once a year and re-do them. Seems like it usually, but not always, happens during the depths of winter, when my hands get especially dry.
I’ve always used my index finger as a Touch ID on my iPad. It probably works about 50% of the time. I’ve gotten so used to having to manually enter the passcode I don’t think much about it any longer.
I love Face ID on my iPhone, though. It works wonderfully, almost 100% of the time.
Since i got an iPad Pro 1st generation 7 years ago i have had problems using touch. Sometimes the iPad would respond, sometimes not which was very frustrating; bought a pencil and things were fine. Same problem on the iPhone. I do notice the better half’s 2019’s iPad Pro is more sensitive. My 2022 MBP does respond to my index finger, but i have to press very hard on the Touch ID key.
Not sure if this has any bearing, but 240v ac does very little to me, i generally get a slight tingle. Farmers get a shock when i grab and hold onto to their electric fences; they rush of quickly to make sure they are functioning properly, especially if they have an aggressive bull on the other side. My fingers do get cold very quickly and turn white from a lack of blood, probably caused by CLL.
This discussion reminds me of a scifi novel (Asimov?) where robots didn’t realise they weren’t human until some strange things happened - such as no fingerprints! 
I have had reasonable success with touch ID on various Apple devices but home renovations tend to cause problems with my fingerprints worn away.
Thank you all for your comments. It seems that my problem may be
Hands abraded
Pinky can no longer cover the home button completely
(Wonder if 30 kg weight loss causes fingers to shrink)
The summer season and my work on our boat……
I will admit that in the past 3 months, have had to redo my fingerprints at least 4 times.
Also, I have come to believe that putting into the phone two versions of the same finger so confuses the software that it just rejects both, either etc etc.
Again thank you. As for unlocking with my face, I think that if I ever get a phone with that option I would probably scare it to death! 
It most certainly can:
I’ve found (on my HP PC, with its fingerprint reader) that moisture can have a big impact. If I recently washed my hands, I need to dry them (wiping them on my pants usually is enough) before they will read correctly.
If you’re working outdoors around your boat, then water and humidity will almost certainly impact the quality of its readings.
FWIW, I was nervous about FaceID, but it’s now been nearly 2 years since I got my iPhone 13, and it works very well. Even in a dark room, because it is using IR for the scanning. I haven’t found any problems, but there are a few minor annoyances:
I have 3 TouchID devices, an old iPhone, an iPad, and a new M1 MacBook Air. TouchID only works reliably on the iPhone. The other two devices fail to recognize my finger after one or two successes. On the whole it’s useless. The fact that it works consistently on the oldest of these devices suggests the problem is not my biometrics but the devices.
I have FaceID on my new iPhone and it is superb. I hope Apple makes this (retrospectively) available on Macs with the new version of macOS.
Touch ID has never worked well for me on my 15-inch MBP. It works two or three times, then never works again. If I reset it, the same thing happens. Personally , I don’t understand why Face ID isn’t implemented on all Macs. For me, it works flawlessly.
To protect my skin, I use “Gloves in a Bottle,” a silicon lotion which dries on the hands, and as result, I’ve never been able to use Touch ID with anything. Could it be something like that?
I’ve had problems with Touch ID on my iPad Pro (1st Gen) in the winter in recent years, but not in the summer. So far, after two winters I’ve not had any problems on my 16” MBP (M1). I suspect extremely dry air for a prolonged time, and the age of the sensor may have something to do with it. Last winter I took my iPad to an Apple Store and they said nothing was wrong with it, and when spring arrived, the problem went away on its own. I don’t recall ever having problems with an iPhone before Face ID.
Yes, yes! I’ve never had Touch ID to work very well at all. I’ve had it on two iPhones in the past, and currently on my M1 Macbook Air, and my current iPad. I’ve ended up disabling it. It’s faster just to put in the passcode without fooling with it.
The pattern is always the same: after initial training, it works almost always, but then it gradually degrades until finally it works maybe 30% of the time.
I’ve tried being really conscious of angling and positioning my finger in all likely ways during the setup, and also the trick of programming the same finger as multiple fingers to increase the chances. Also using different fingers. Same result.
Face ID is always flawless on everything. I actually wish I’d bought an iPad Pro instead of an iPad Air now just to have an ID technology that works.
I notice several others commenting about the initial success and then it going downhill. Any theories on why that could be?
I have given up on Touch ID completely, which means at least one extra step for every transaction with typing in a passcode each time. I put it down to being a guitar player but more so to getting older as fingerprints seem to get less obvious with age - surely something Apple designers should be able to figure out - or are they just young and ageist.
I definitely sympathize with those for whom Touch ID is not reliable, even though I strongly prefer it to Face ID. In a perfect world, we should have a choice.
I’ve known people who have difficulty activating non-mechanical touch-sensitive elevator buttons. I wonder if they have similar issues with Touch ID.