We import data from your connected integrations as variables - some common ones are "title", "first_name", and "city".
If you see a red "not showing" stamp like the above, this is because one or more notifications from that integration do not have a valid value for a variable.
Events with this red stamp are not displayed as notification on your site live.
For occasional "not showing" warnings, find the offending Template and use a Template Filter "fallback".
If you are consistently seeing this red error and you believe the variable should be captured in the integration, ping us at firstname.lastname@example.org so we can investigate further.