I have the same problem. After biking for 8 hours in the rain yesterday using my iPhone 7 continually (for delivery navigation), this morning the haptics in the home button didn’t work. I tried again and it worked, but since then no go. Neither several hard restarts nor restarting a few times in General work either.
I’m forced to use the virtual home button. Touch ID does work though, as well as manual ID.
Another detail that may be interesting is that the phone was charging from a power pack more or less the whole time yesterday (since the battery isn’t what it used to be). Temperature about 6 C.
From what I’ve read today on the internet, rain/water may be an issue in this problem.
The only other thing I know of to try is OS upgrade. I have iOS 12.4.1 installed. 13.1.2 is available but I’m going to wait a while until Apple stops pumping out bug fix versions.