why would my previously reasonable sleeping 14mth old suddenly start waking at 11pm and not re-settle

[Tiredemma]

Wide awake. Won't settle. I'm exhausted.

Previously an ok sleeper but past three nights horrendous.

Hashe just started walking?

Yes. This week

Think it's (change in sleep) often due to a mental or physical progression, have you read the wonder weeks? I think best you can do is get to bed early yourself for a bit and keep night time as dark and boring as possible? I read no cry sleep solution with ds1 when he did similar? Getting them to bed early can help them catch up too, or make sure her daytime naps are sufficient to recharge her batteries?