I can't get WiFi on my phone

I can't get WiFi on my phone

Did Tech Support for an ISP

Customer: "I can't get WiFi on my phone"

TS : does routine checks, remote login to router, etc....

TS : "All looks OK here. Can't see your phone connected to the router though I can see a computer and a TV box connected on Wi-Fi. Any errors on the phone?"

Customer: "It looks OK. It worked fine yesterday"

TS : does a bit more digging - can't see a problem

TS : "can you move closer to the router?"

Customer: "I'm in Spain on holidays - the router is back home, would that make a difference?"