I have faced the below error when using Instagram Block with the WordPress’s new editor, below is the screenshot of what happens when you try to embed the “Instagram Block” on Self hosted WordPress site
This image uses Instagram gutenberg Block.
In this image when I pasted the url it this error.
To solve the above issue you need to use “Custom HTML block” instead of Gutenberg block, and add the HTML embed code from Gutenberg.
Please follow the below screenshots for Embedding the HTML BLock for Instagram.
Hope this post will help you, let me know in comments.