Welcome to the Forums. It takes quite a while for the data to be imported. I joined about ten days ago and had to wait a few hours (IIRC) to see what I was expecting. It can help to select the ‘Refresh profile’ link under your profile image and level info on your profile page there.
Concerning data for building up your power profile (races and group rides only, not free rides), it only includes rides from the day of joining and after, so depending on whether you’ve ridden in the previous hours, you might indeed have nothing until you next ride, plus the time it takes ZwiftPower to import and crunch those numbers.
You should see free rides and other previous group rides, etc., under ‘Activities’. I don’t know what’s normal, but I only see Activities going back about four months in mine, plus one random ride from my first week on Zwift (April 2019).
As others have pointed out recently, ZwiftPower was a purely volunteer/community-produced and managed platform until end of 2020 (when Zwift acquired it - and haven’t built anything new into it, apparently), so although it doesn’t have the most user-friendly layout and interface, it’s still pretty good for a free resource.