"Can't make a group of objects that are within different groups"

I have been trying to group some paths together for several hours now but I just get this error message. I have ungrouped using the ctr +  shift + g and there are no groups when I look through the layer. It is just certain parts of my illustration that arent grouping whilst there is no issue in other parts. I have just started out so I have no idea what I am doing wrong. I have used the image trace to create the illustration if that makes a difference. I have tried using the lasso and the group select but neither seem to work.