Port forwarding cannot be set up

[#1]

I have a Plusnet Hub One.  About a month ago, I successfully set up port forwarding but today it wasn't working anymore, so I deleted the configuration and tried to set it up again.  I went to [Advanced Settings > Firewall > Port Forwarding > Manage games and applications] and added a new application allowing TCP on the required ports.  This worked fine.

I then clicked "Back to Port Forwarding" and tried to add a reference from the application to one of my devices.  I chose the Application and chose the Device and clicked the "Add" button.  There is a notification "Changes applied" written in green below the "Apply" button but no other GUI changes.  I then click "Apply" and again no changes.

Previously, the new registration appeared below the row where you add one.  So something is not right.

I restarted the router, and tried this in 3 browsers - Chrome, Firefox, Edge.

[#2 · Accepted solution]

I eventually got it working.  The standard keyboard shortcuts such as pressing Space to click a button do not work as expected. I had to do the whole thing with mouse clicks.