If during the upload process you are unable to click the continue button after uploading your files (if the files have uploaded successfully the check marks next to the files will turn green) and choosing a name for your project you may want to double check if you are behind a firewall or proxy.
We use Filestack for our filepicker, they have some documentation over here that might help: https://www.filestack.com/docs/knowledge-base/general/firewall-issues-and-whitelisting
If you are in a rush to get your project uploaded we'd be happy to upload it under your account on your behalf. Please just send us the files either via chat or to firstname.lastname@example.org.
If you know you are not behind a proxy or firewall and are experiencing this issue, please contact us.