You can still access your PMs from the old site at legacy.curseforge.com/home/private-messages.
This is something we'll be tackling in the future, but because the old site is still active for other games we can't migrate them yet. :)
Some repositories are still importing, if you can confirm which projects you're not seeing yet please let me know. The localizations should also be imported so if they're missing please let me know on which project.