This was the only reason I was keeping cable. Years of watching on my phone and iPad, now nothing. Yeah. Spent an hour of the phone with customer support about it today - they killed live streaming ability from the TV apps without bothering to give anyone ANY notice. I only watch tv from my phone and iPad because I'm on the go a lot so I just switched to SlingTV today for a quarter of the cost.
On my SECOND phone call to Comcast customer service, the guy stayed on the phone with me until we had a resolution and he said, after 22 minutes that most people stream tv from the website on their computer and not the apps so they were killing the apps' live streaming abilities (he said that the apps will only be for on demand movies etc) and directing people to online website tv.xfinity.com WHICH DOESN'T WORK ON SAFARI OR CHROME ON MOBILE DEVICES and that he was very sorry.
I'd like to look into your issues with live streaming on the mobile app.