Do not use the Share to YT feature in MEP. YT keeps changing the way it's done and the program can't keep up. Old programs are not going to be updated just because YT changes the parameters.
Export normally, review, correct, export, review, correct... When you are satisfied, go to YT and Create - upload your video and add in all of the information.
Google (YouTube) regularly changes its upload protocols, with the result that all recent versions of Movie Edit Pro, now called Movie Studio, have dropped the option to upload directly to YT.
The best solution is to save the exported video to your own hard drive and then use YT's own uploader to copy it to your account on YT.