Your account is in good standing, as determined by the YouTube Community Guidelines.
You verify your account with a mobile phone.
Your account has no worldwide Content ID blocks on any content
On the upload page, click the link to Increase your limit to be prompted to verify your account. If you do not have the option to verify your account, or if you lose your access to long uploads, the best first step is to check your account for copyright claims and strikes.
Recoverable and longer length uploading with Chrome and Firefox
Chrome and Firefox 4+ users can not only upload files of a size up to 20GB, but it is also possible to resume uploads if your connection drops, and recover uploads even if you leave the page. When you return to the upload page and attempt the same file again, the progress bar will jump to where it was before.