Can't chromecast streaming services on T-mobile Home Internet

I am having the same issue. Good thing i have not gotten rid of my other network as it works fine there. 
Have been trying to search the internet for something but so far no luck, as you said i can cast my whole screen but if i want to cast from youTube the sreen just goes black and then says it cannot connect.
This is the second issue i have had, the first was live hulu tv which will not work either (there’s a thread on that if you search)
I am going to keep digging and if I find a fix ill share it here.