I had this same issue. Here's exactly what I did, hopefully this will work for you too.
1. Activate the phone using the "temporary" number that comes with the new line (support will ask you to do this)
2. Reach out to support using the app - the wait time is extremely long right now, but with enough patience, you will get connected to someone eventually. Try to keep the session active so that it doesn't time out - I did this by minimizing and maximizing the chat window every few minutes.
3. Once you get connected, they can port over the number very quickly. Be sure to have your previous carrier's account number and port-out PIN number.
4. After a few minutes (in my case) I got an email and a notification from the app that the port was complete. It did take a few minutes after those notifications for the service to fully activate. But from the time of porting to full activation, it was only like 15 - 20 minutes.
Hopefully this works for you all, this seems to be a widespread issue 🙁