To track data properly and enable Symphony Conversions, you'll want to ensure your Pixel is linked to your ad account.
Connect your Facebook Pixel to your ad account
Navigate to your Facebook pixel settings here.
You may be prompted to select your business before your pixels are shown.
Select your Pixel under the Datasets section on the left.
Click the Connect assets button under your pixel's name.
If the Connect assets button is greyed out, you most likely don't have access to the pixel specifically. Follow these steps to gain access.
Click Other business assets.
A list of your ad accounts should be shown. Find the ad account you want to connect your pixel to and select it, then click Add.
You should now see the ad account under Connected assets in your pixel.
Head back to the Advanced Settings tab in Symphony and click Verify Connection in step 2 to proceed.