I sorted horribly tight ankles in about 2 weeks using this:
Wrap a band around a post.
Then around one leg, just above the ankle
Step away from the post (face the post), putting lots of tension on the band
Get in a proposing position with banded leg forward
Push your knees forward as far as you can (push on your knees with your hands)
Return to start position
Perform 20 reps
Repeat on the other side
Repeat again on both sides, this time facing away from the post.
The other thing to look for is lack of internal rotation of the hip (easy test is lay on your back, legs straight out. Bend one hip and knee at 90 degrees. Twist your leg so your knee stays where it is (and at 90 degrees) and your ankle moves away from your body. If your lower leg does stick out to 30 degrees, you have an issue. Another dead give away is if you need to point your toes way out to hit depth). Use band distraction for this as well - search YouTube