Youtube app problems

My phone (Samaung Galaxy Core Prime) is relatively new and apps like YouTube, Gmail etc. were already downloaded and I can't uninstall them or anything. Anyway, YouTube is banned where I live and I can't access it on the net unless I open a proxy site, so it shouldn't work on the app right? Well I tried playing a video on the app like weeks ago but it didn't work.....
Last week however, everu video I searched for was playing perfectly! I was glad I could use YouTube.
But it isn't working now :( For a week it hasn't been able to play any video, what could the problem be? I haven't updated the app incase it stops working, but it still stopped! How can I get it to work? Please help, I'll appreciate it, thanks.