Same problem occurred with my Rog phone 5s. After the last update, wifi stopped turning on, had to send it to Service center. Sent on 10th October, 22 and got repaired set back on 31st October, 22.
No money was asked as the set is in warranty, but as I checked this forum, almost all 5s users had similar complaints.
Service was prompt and good but if this was a known issue with a specific update, it could have been avoided.
A little disappointed with Premium phone makers like Asus.