I've been researching this problem for quite a while. Although I haven't pinpointed any possible solution yet but here's what I have noticed:
The videos on the YouTube app don't always fail to play with the classic "cannot connect" message. It only fails when I'm using wifi at home with my ISP. If I'm staying at a friends house with Different ISP, it works Like a Swiss watch.
Now whether my ISP somehow blocks most videos on YouTube is a weak claim, note that whenever I try to load the same video a couple of times, it works. So there's some sort of delay.
My question is, with my current set up, is it possible to port forward the YouTube app on my iPad through my wifi modem. Has anyone done it before???
Appreciate any feedback!