Milk can be difficult to remove if spill is substantial.
- For the enzyme to work it needs a decent dwell time.
- If in pad, I doubt the enzyme reached all the way through carpet (+ it is also in glue layer).
- You can encapsulate or bonnet, but if milk remains in pad, it will start smelling later.
If you can access pad, take care of it, clean carpet from both sides. It would work but be lots of work.
Otherwise give a good dose of enzyme, dwell time, a mini flood and flush with the claw. Follow with lots of dry passes. And if it makes you feel good follow with encapsulation & a bonnet.
I don't think it is a dye stain as it came back.