9 month old still not crawling

I feel like this question is posted almost daily so bare with me, but is are people’s 9 month olds still not crawling? My daughter is 9 months on the 30th and still just scoots around in her butt. She’ll get in the position a little bit but then her legs go out from under her and she screams she’s on her tummy. Are there any tips to help her?

My husband is terrified she’ll learn to walk first because his sister told him researchers have found that babies who never crawl can have developmental issues.