The child might be having nipple confusion. Use feeding bottles with nipples of the same consistency as yours. It may sound weird, but check the nipples of feeding bottles for texture, size etc.
Some babies may have difficulty drinking from the bottle because the milk does not flow properly. Airflow is important so the milk will flow easily.
Check your feeding schedule. Whether you're breastfeeding or using a bottle, make sure that you feed the baby at the same time, same location if possible.