Just an update to this one as I had a unique issue from not using my keyboard for a month, somehow the battery connection part in the back of the keyboard had some rust build up which I needed to clean off so that the batteries could actually have a proper contact to the metal and as soon as I cleaned that off it started working.
This is obviously a very unique situation but could be worth checking inside as I was doing everything in this thread and I took the batteries out again to see if that would do anything and randomly spotted the rust build up.