It is quite common for babies to go through phases of bottle refusal, even if they have taken one well in the past. If your baby is around five months old, they may be experiencing teething, which can make sucking uncomfortable due to sore gums. Consistency is key; if bottle-feeding is infrequent, babies may lose the habit or grow more sensitive to changes in nipple flow or temperature. Try offering the bottle when they are calm rather than extremely hungry, and consider using a teething toy to soothe their gums before feeding to see if it improves their comfort.