First, verify that you've updated the app. If you're running the latest version, ensure that your profile is not set to Private. If it is, you can't see who viewed your profile. If that still doesn't work, investigate whether parental controls have been activated for your TikTok account. If that's the case, your profile is automatically set to Private, and you won't have the option for "Profile views." You can also try reinstalling the app to fix temporary glitches with TikTok.