Headliner Glue

Ok 63. That helps some. What model? I have done about every make and model headliner install and there are many different methods conceived by the manufacturers. This also changed with eras. I could use more information to help you best.
Most all cars have the noise reduction insulating pad you mentioned regardless of style
of headliner. Good that you replaced it. The carpet pad you used works fine for this. Some cars
used a tar paper.
Does your car have wire rods or bows that hold up the headliner fabric or is the fabric glued to a panel. These are the two most common methods.
If the glue is being absorbed into the fabric and showing thru the finished side it must have a
cloth fabric rather than vinyl? The older cars had mohair and this could happen. Mohair
headliners are generally the bow type and will only need glue around the perimeter.