When I try to connect via personal hotspot using the Instant Hotspot feature it fails to connect. I have to turn Wifi off/on on the Mac then select my iPhone from the general Wifi names list. Sometimes that also fails and I have to flip the Personal Hotspot toggle on iOS. It never instantly connects and always takes a few attempts. It did work fine prior to High Sierra. It's almost like the Mac doesn't actually recognise my iPhone all the time. Things like Handoff work correctly though. Any suggestions?