If the baby still cannot crawl at 11 months of age, but can maintain sitting balance as well as stand alone, etc., without abnormalities in muscle strength and tone, this is normal because crawling is not an inevitable passage through all motor developmental milestones, but crawling is beneficial for balance, coordination and intellectual development of human development. If a baby still cannot crawl at 11 months of age, cannot remain sitting and standing alone, and has abnormalities in muscle strength and tone, there are high-risk factors before, during or after birth, such as prematurity, low birth weight, and hypoxic-ischemic encephalopathy, etc. If you have any of these manifestations and medical history, you should seek prompt medical attention.