Tailgate switch/ number plates lights not working ...help!

Hi folks, new member here from the UK.
I'm after a little help and I'll tell you my story

I have a 2013 Santa Fe and about 3 years ago my boot switch stopped working. It was out of warranty so I decided to investigate myself.
I removed the switch and noticed that the red cable has become warn and parted so I decided to re dress it and use a butt connector and spliced it together and this worked fine.

About a couple of weeks ago it started playing up again so I had another look and it hadn't changed so again I decided to put a new connector on. This is where it all started going wrong .
It didnt work straight away when I connected it so I started rubbing the two ends of the red wire together and it burst into life !! I connected and it worked for a couple of days then the same happened and I did the same thing.
It has totally failed now and so have the number plate lights?

I have chased the cable back and checked the connector and it all seems ok. Cant see any other damage.

I out my multi meter on the red cable today and it didnt read anything? Is this normal or should the switch have a constant 12v feed?
I was hoping it was just a blown fuse that fed the tailgate switch and the number plate lights but I cant find any info.
I cant drive my car at night now without the number plate lights and climbing into the boot to open it is a pain.

Can anyone help please!

Thanks

James