tl;dr - if a property is not set for a profile, you cannot rely on filtering based on that profile having or not having a certain value. The way Klaviyo handled it changed. Be sure to read this: https://help.klaviyo.com/hc/en-us/articles/14837232353691
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This is an advisory for people who may have found themselves in the same situation.
I’ve recently discovered that I’ve not been emailing many subscribers that I should have been emailing. This comes on the heels of a problem we had with flow conditions, where they were not triggering for people they should have triggered for.
The underlying problem, in both cases, is Klaviyo’s handling of properties which are not set.
With the flows. the person who set them up had put in a filter which prevented people in one flow from entering any other - when a flow starts, it created a custom property against the profile, which the author intended to use to keep people in one flow only. Other flows had a check - exclude people if name-of-custom-property = 1. Problem here was that if that property was not set, then that check was returning true, and thus nobody was entering any flows.
I’ve just found a similar problem with our main segment. We had created a rule a while ago that excluded some customers in a certain country. This worked fine until the change, when it also started excluding subscribers if their country was not set.
I have noticed now and corrected this to ‘country is not set or country is not one of this, this or this’, but seriously, this is really unintuitive and it has cost us potential sales.
If a conditional check is ‘country is not one of these countries’, then if country is not set it is by definition not one of those countries. Someone’s country cannot logically be a certain value if it is not set at all. Most programming languages would either fail and report an error (calling attention to the problem and forcing an investigation) or return true and log a variable does not exist warning to the user.
Anyway, Klaviyo’s change is explained here: https://help.klaviyo.com/hc/en-us/articles/14837232353691
Question for Klaviyo: did you tell people about this change when it happened? I haven’t got an inbox going back that far so I can’t check.