If you don't see the specific social media pages on "connect your social media profiles" page or when connecting your Facebook and Instagram accounts does not work, do the following:
Go to Brain AI tab that's showed as a brain icon (app.sintra.ai/brain)
Click on the social media integration that is not showing the page
Disconnect it
Click "connect"
You will see the previously connected account - click the trash bin icon next to it to remove the connection completely
Set up the integration again.