How are you uploading to YouTube?
which platform are you on? What is the error message you are seeing on exporting to desktop or to YouTube? If you are on Windows platform, can please you try exporting to desktop after unchecking 'Use Hardware Acceleration' from preferences?
What is the duration of timeline and is your google account a verified one? By verified, I mean is your account linked with phone and you entered code sent to your phone number to your account page. Google puts some restrictions while uploading the video based on the verified status of the account.