It says Continue without disabling on the bottom of that banner, which if you do, it gives you access to the whole site without hassling you again. At least it does on my end with Firefox.

Obviously it’s bullshit to constantly badger you, but it doesn’t currently restrict access to anything.

Did you recently stop paying for fitbit premium or have the free trial expire? This happened to me when my free trial expired.

What fixed it for me was restarting the watch. I’m back up and running and my deep sleep and REM cycles are working again. I’ve heard if that doesn’t work, you can un-pair the watch, restart it and re-pair to your phone and it could fix it. Good luck!