Fans not being recognised in SignalRGB

Hi,
I have had an issue where some of my fans in my pc aren’t being picked up by SignalRGB. In other programs they work but, in signal I’m having issues. They’re in a column of 3 fans and the bottom one has no rgb. I have 2 columns of 3 fans and it’s just the end ones that don’t work with signal (if that makes sense) any advice?