there was a small update shown on Garmin Express
I don't believe it's related to the Garmin Express update. I'm having the same problem and I haven't updated Express yet. There's a thread on Fenix 5X/5S forum where some are having the same issue and it's suspected to be related to FW 12.50. I'm not sure, but I thought I used Wi-Fi successfully after 12.50, so....?
Not sure what the problem is as I was connecting fine until a couple of days ago. Error message I get is "No app or Wi-Fi Connection available when I try to sync from the control, or 'No down wifi connection available' when I try to connect.