Earlier, the boilerplate code got automatically completed after writing <DOCTYPE html>, but now it's not working and I've to write the boiler plate code myself every-time.
I've tried:
- Using HTML snippets package.
- Uninstalling packages.
- Re-installing Vscode. Nothing seems to work.

Any, help is deeply appreciated.
I am all new here, so if any sort of mistake is done by me in asking or specifying the question, I apologize.
I had this problem too. You need to change your language mode to html first. Then using
!will work. The location of language mode is in the bottom right corner of vs codeI ended up installing HTML5 Boilerplate extension by sidthesloth. The boilerplate was a bit more complete.