This is an accepted solution.
Thank you for taking the time to reach out on this thread. As mentioned above, these steps were for the previous Facebook Shop channel, which was replaced by the new Facebook channel last year. There is a new process for troubleshooting these syncing errors for the newer channel, which requires having our technical team look into that for you. While we’re not able to provide account-specific support via the Shopify Community at this time, we’d be happy to continue assisting you through live chat, email, or callback. Please visit https://bit.ly/3cJkx8V and log in to your account to create a support request. As the steps in this thread are for the older version of the channel, I will be closing this thread for any future replies. Since contacting support is the next step, I've marked this reply as the solution for the benefit of others who may discover this topic. Thanks!