
Have you tried expressing a little milk from the nipple so she can taste it there and then holding her there while she feeds?
Are you making sure that the
whole of the nipple and surrounding area are in her mouth?
Also try stroking her under her chin and throat while at the nipple, this can stimulate suckling
She may be exhausted from the birth

I had one like this, she was 'flat' but with a pink tongue and we had to work on her to get her breathing. Had been the one behind the one that took ages and came out 10 minutes later without even a push. She was a bit sleepy at first and needed encouragement to feed but was fine after the first night.
Hope this helps
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