If you have not recently rebooted your machine please give this a try.
The VPN client can sometimes fail to disconnect cleanly and will not connect again until a reboot has cleared the previous connection.
If your device can't see the VPN servers then connecting is going to fail, a quick way you can check is by trying to go to https://vpn2020.uea.ac.uk in a web browser.
This should redirect you to the UEA login page, but if it gives you a DNS error, or times out when connecting you should try to clear your static routes (instructions further down this page).
Here are some things to try if the VPN client is failing to connect.
As the traffic from your VPN client needs to go directly to the servers, and not via the VPN, it creates static routes that force this, but if these aren't removed correctly and your device changes address (for example, you connect at UEA or elsewhere, then try from your home) then it can no longer communicate with the servers.
Sometimes disconnecting from the Wi-fi and reconnecting can clear these, but if that doesn't work then rebooting the machine is the quickest way.
If some software is persisting these routes between reboots then you'll need to clear the routes manually.
Disconnect from the Wi-fi, plysical network connections first.
That way when you re-connect after clearing the routes it should add in any that are necessary.
Mac OS
You can check the routing table with:
netstat -nr
If you see static entries in there for destinations of 139.222.247.192 or 139.222.247.255 then you will need to clear your routing table.
Open Terminal, run this command, you will be prompted for the password to your machine to run it:
sudo route -n flush
Windows
Open a command prompt, or powershell, prompt as an administrator (search using the start menu, the right-click on the result you want and there should be a 'Run as administrator' option).
ipconfig /flushdns
route -d