Fenix 5 plus stopped connecting to Android Garmin Express

Just typical

My Fenix 5 plus has been working fine with my phone since new.

I am now out of country and using it quite extensively to navigate. I do not have mobile data on my phone as I am roaming but do have access to a WiFi hotspot 

Today I noticed my watch was not connected to my phone after several days of working fine out here. So I tried disabling/enabling Bluetooth on my phone and killing Connect. This did not solve so I rebooted both the phone and the watch. Eventually I tried removing the app data and removing the watch from my devices in both connect and the Bluetooth settings. The watch does not want to repair with the phone and just says waiting for phone.

Is there anything else I can do to get this working or is it something to do with having no mobile data, despite having WiFi. I have never had this issue traveling abroad before though.