This is from my host provider: How and where do I fix this:
It’s trying to request https://cdn.www.mydomain.com/wp-includes/css/dist/block-library/style.min.css?ver=5.5.3, but this does not exist
www.mydomain.com/wp-includes/css/dist/block-library/style.min.css?ver=5.5.3 does exist though. Try to fix the .cdn or remove it all together and it will work just fine.