Double check that “Use legacy editor” is turned off (I’m pretty sure it turned itself off for me after the last update, and this was hinted at in the release notes for v0.13.9)
Make sure you have restarted after updating the setting
Check that you are actually in “Live Preview” mode instead of “Source View”, either by toggling the mode using the 3-dot menu, or the command palette (“Toggle Live Preview/Source View”, which I have bound to a hotkey to allow easy switching when necessary)