Hub 4 modem mode

See below, see note 1: 

How to put a VM hub into modem mode:

1) Access your hub on 192.168.0.1, sign on and put it into modem mode. On the Hub3 the bottom LED will change to magenta, on a Hub4 the LED band will be green, on a Hub5 the LED will be green. Best done from a wired connection.

2) Turn off the hub and disconnect any Ethernet cables

3) Fully initialise your own router or mesh master unit and make sure the WAN port is set to DHCP (for some routers or mesh this may have to be done in router mode before entering modem mode)

4) Connect your router or mesh master unit to the VM hub with an Ethernet cable, Cat5e or Cat6, any higher specification is a waste of money. On a Hub5 use port 4.

5) Turn on the VM hub.

6) You should now be able to access the internet and the hub will now be on 192.168.100.1

Note1: this only needs doing once for each new router or when VM changes your WAN IP address.

Note2: If you have a Hub4 and your own router is NOT 192.168.0.1 then it’s possible that you can still access the VM hub on 192.168.0.1

I'm getting a bit confused.  When in modem mode you are aware you can only use one ethernet cable, and that cable goes from the Hub to the WAN port on the TP-Link Router?

This might sound weird, but I've had issues reconnecting in the past when in modem mode, then it magically fixes itself after a couple days. I don't have any explanation other than I can see my router sending DHCP requests but it doesn't get a reply, then all of a sudden a couple days later it'll get a reply and the connection will come up. As you posted this a couple days ago, you might be on the threshold of this all springing back into life again, let us know how you're getting on.

When this happens to me now I have a USB dongle with a 4G SIM that I use, my router is a Draytek Vigor and will failover automatically to the dongle if/when the fibre goes down, so it's not a massive issue for me in the meantime, things just run a little slower until the fibre comes back up.

VM might have DHCP problems and the router mode may not care if it can't DHCP and just stay on the same IP till DHCP is up and running its a bad thing to do and VM should fix it. However if you go from modem mode to router mode then how can you get a IP? unless the hub stores the last know IP for router mode but then what happens if you reset the hub? then your stuck! and VM solution is to send another hub because we would not understand the the problem just well we send them a hub because between then and now the real fix would of happened?   

I fact thinking about if the above is true if you know your last WAN IP in modem mode should DHCP be down you can put it in as static and see if you get back on line.

A small point. When going into modem mode the VM hub after being setup must be powered off. Power on all equipment connect, but not the hub. The hub MUST be the last device activated.

New hub arrived , after swappping it out for the old  one put into modem mode everything worked pefectly must have been shardware problem with old hub .

Thank you all  for the reply and possible solutions