iPhone 8 Taptic Engine not working after official battery repair

(For people finding this post after having the same issue)

The support chat I mentioned was completely useless and I was ignored after I told them that it was impossible to do a software update

I went to the Apple Store next day and told them and they luckily booked a priority appointment for that exact time, though usually you would need a pre-booked appointment. Told them the issue and how they had likely caused the issue after the repair they did and they took the phone for an hour and a half, telling me it would be for free. Came back to collect it and it all worked fine, but be warned that you may have to tell all staff you talk to about the fact it was their fault and you were told you would get the repair for free, as the final staff member I spoke to was prepared to charge me the full price for the repair.

In the end I got it back fully repaired for free and so far (for the past few hours) it has been fully functional and has passed all tests.