Your Youtube player app give you error but when you at the same time open youtube in browser it start setting played
You will see many forum explain different type of procedure but they are actually not aware of the reason why this happen and tell you some Wipe your data, or Clear Cache or Uninstall your Youtube and reinstall — This some time work in some mobile but its a not more than a nonsense.
WHY THIS HAPPEN ( YOUTUBE PLAYER STOP WORKING and AFTER SOMEDAYS START WORKING).
Youtube show ads, so many time you install third party application they have feature to block ads and when you open youtube player it start howing ads it get blocked by ads blocker and you get error CONNECTION TO SERVER LOST . TOUCH TO RETRY, if you uninstall the thirdparty app like Ccleaner, 360 Securty etc but their ads blocker many time remain in your phone. So you have to remove it for that YOU HAVE TO ROOT YOUR PHONE (COMPULSORY).
After you rooted your phone you have to install a app which remove the ADS APP install in your phone and Your Youtube player will start instantly.
THIS METHOF CAN ALSO BE FOLLOWED ON CUSTOM ROM BECAUSE THEY ARE ALREADY ROOTED.
DOWNLOAD DOT PROXY SOFTWARE