Facebook publishing is not available on the Sitebuilder Classic platform anymore because Facebook has deprecated this functionality. The Publish to Facebook tile is about to be removed from the dashboard.
In September 2022, Facebook announced that the Pages Custom Tab API features will no longer be available via GraphAPI. As they roll out the new Pages experience, there are some Pages API features that will be deprecated.
This is why the Pages Custom Tab feature is not available anymore for the new pages. And the feature for the existing pages will be fully deprecated by December 14, 2022.
For the Sitebuilder Classic users who had used this feature before, we recommend deleting the website tab from the Facebook Business page. Here’s the instruction for this.
And as an alternative to the disabled feature, we can offer the Online store owners to sell their products on Facebook by automatically uploading and syncing the store product catalog to the Shop section on the Facebook business page.