My old theme not support all Gutenberg Blocks

Hi,
I have a private theme years ago

now i tried Gutenberg Blocks and i like it

But some blocks didn’t work such as : youtube and reusable blocks

youtube : show the url not show the video so i used youtube code
Reusable blocks : show nothing

1 – I disabled all plugins and the same problem then active it again
2 – tried another theme and Gutenberg Blocks worded fine

so i’m sure these is an update code that i have to use in my old theme to support Gutenberg Blocks

any help

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