Many Videos dont play since v13.11

Since the 13.11 update, many videos no longer play.

Symptoms: open video, window goes black and tries to play lead-in advert. Nothing happens.

I have:
0. checked I have the latest iOS for my device
1. deleted cache & cookies
2. hard reset iPad
3. deleted and reinstalled YouTube

This is:
IPad4
IOS 10.3.3

Note: same video plays on my ancient iPhone 4s without problems.

Asmilwho about YouTube - Watch, Upload and Share Videos, v13.12