'Preview Article with Blocks' link is missing
No 'Preview Article with Blocks' for certain users
Cannot preview knowledge article with blocks
The user's language preference setting was set to 'NUL' which is invalid
Invalid language preference setting in the sys_user table
Check the sys_user record of the user having the issue. Check the language settings (Language/preferred_language) if it is valid.
Change it to a valid language and try again