Adding a virgin media WiFi extender has killed my 5GHz WiFi network

I have recently moved house and put in a new Virgin media system the Wi-Fi router is a hub 5

It took me a while to get everything configured. I had to split the Wi-Fi networks into a 2.4 GHz band and a 5 GHz SSIDs because I have many legacy devices which only work on 2.4 such as smart plugs. As well as configuring the hub 5 of course there are countless devices around my house some on the 2.4  some on the 5 GHz network.

When I ordered the package I was interested in the Volt upgrade because it came with up to 3 Wi-Fi extenders and I knew I would need these because the Wi-Fi coverage to the back of my house is problematic 

The first one arrived today and I plugged it in and it did its thing and seem to just work, I was happy for the whole of about five minutes until I realized that the 5 gigahertz Wi-Fi network had been killed by virtue of adding this extender, and all my devices in the house which are on the 5 GHz network are now showing as being offline 

It's going to be a lot of effort going around them all putting them onto the 2.4 gig or... (and this is my question ) can I simply re-enable it in the router configuration as it was before I added the Wi-Fi extender and will the Wi-Fi extender still work with the split SSIDs, will it extend both SSIDs.

If anyone from Virgin is reading this I will share that I take a very dim view of this, if the Wi-Fi extenders cannot work with a split network then there should be a label or warning as such on the box. It would have been preferable for the Wi-Fi extender to literally not have worked then to have had it work but to have it also  mess up my carefully configured router in the process