HH5 not sharing Mobile WiFi

I've moved into a short term house so I don't want to connect the phone and internet due to the length of contracts. I'm using a wireless 4G mobile WiFi and I want to use my HomeHub5 as the network router. I've connected the HH5 wirelessly to the mobile WiFi and ifI test the connection it can ping the internet. I've associated the connection with the LAN and removed the firewalls but it's still not sharing the internet over the HH5, any suggestions please?

Thanks
Lyle

Obviously mobile connection has to be in WAN.

Unless you run the HH5 in dumb AP mode.

https://openwrt.org/docs/guide-user/network/wifi/wifiextenders/bridgedap