Connect to Wifi Extender via Mifi

My Internet is via a Mifi Device ( modem) from Vodafone.

I have just upgraded the Mifi, the device is working to connect to the internet.

I now cannot connect to the extender. (AC1200/EX6130 Wifi Range Extender - the model was not in the drop down list)

I cannot connect via WPS, as the modem does not have a WPS button.

I also cannot connect with the Netgear installation assistant, because NETGEAR_EXT is not showing up in the connection manager. I have tried it wth the Mifi Wifi on and off. 

I have pressed the reset button on the extender.

I do not have an ethernet connection on the modem. It's just Wifi.

It did all work before the upgrade & the old netgear networks are still showing on my device. My devices are not 'forgetting' these networks, even after I had selected 'forget this network'.

Hope someone can help :)