Oh dear, another g.parent who thinks they know better about a child than that child's main carers (her parents).
Obviously, any of the things mentioned here (glue ear, autism,), COULD be the cause. However, the most probable reason is that the child is just not ready to start to talk yet. Babbling cover virtually every known language, and shows that the babe has th ability to talk.
My twins babbled happily away until they were well turned two years old. There were three slightly older siblings and most of my time (language wise) was spent on rying to etend the vocabulary of the three year old and help the 5 & 6 year olds with their reading skills.
At their two yeawr odl check, the elderly, retired Doctor brought back for Well Baby clinic was alarmed at my reply of ' NONE' to how many words they had. The Health Visitor, who knew me, told him that there were three only slightly older children and I was an experienced Mother and Foster Parent and if I was not concerned, chances are nothing tobe concerned about.
At two years and three months, even hubbie, who usually accepted what I said on child upbringing, was expressing concern. It was a couple of months after that they both started to use words - and then (to my total amazement) within the space of a fortnight moved on to whole sentences being used. When I thought about I realised I had not done much of the single word bit to them.
Obviously okay, as this was many years ago and both managed excellent Backelors degrees and Masters Degrees etc.