Sometimes Facebook's login connection can be finicky, especially if this is your first time running ads or if you haven't run ads using your Facebook profile in a while.
After creating a campaign, sometimes Facebook can "invalidate" an app's Facebook login access, which can be fixed pretty easily by following a few steps.
To re-establish your Facebook account's connection to Symphony, follow these steps:
Go to the Symphony Marketing tab (https://beta.symphonyos.co/marketing)
Click "Increase Music Streams"
Click on any song
On the "Connect Accounts" page, click the arrow or "connect" button next to "Facebook", under "Pages"
Select your Facebook Page and hit "Connect"
Video Walkthrough: