Youtube has an upper limit on filesizes (1GB) and duration (10 minutes) for video. Unless of course if you have a Guru Account with them.
Try rendering out as an MPEG4 or H.264 format with 2500kbps setting. Audio set at 128kbps should be sufficient. Allow for automatic keyframes setting or the default of 50 also works well for most footage. If you have a lot of fast-moving imagery, then lower the keyframe setting to 5 or 10. Alseo, setting the framerate to 18 helps in reducing filesize.
And, in future Qs, please provide more information instead of just spelling out the problem. You would have done better if you had stated the actual export and render/output settings that you used.
HTH
RoRK
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