Same thing happened to me, I tried everything (theme ID in URL, refreshing cache, incognito (which just shows your live theme), updating CLI, etc). Nothing worked except for deleting the .shopify directory and pulling the theme again.
rm -rf .shopify/
shopify theme pull
Remember: This wipes out any current local theme changes, so make sure you’ve backed them up in some way, either copying them to an empty buffer, git branch, git stash, etc, before re-pulling the theme.