If so, it means an ad or keyword which has not been approved yet although the explanation Google provides covers everything except that possibility.
The last bullet "hints" at that possibility but otherwise makes no sense. Why is it that a keyword "rarely included in search queries" will begin showing for this keyword soon? Maybe I'm reading too much into that.
Erik_Jan, if this has been going on more than a week, it's time to contact support. I've had adgroups that were pending review and just somehow missed or forgotten. They never showed for keywords until I contacted support.
On the other hand, it doesn't make a lot of sense that one version of the keyword would show and the others wouldn't were they awaiting approval. Good support question. Good luck! ;)
Another thing to keep in mind is that the Ads Diagnostic Tool is flaky, to put it politely.
When I put the kws I tested at the beginning of this post through the ADT, it said they weren't showing. Message was Ad not shown ¦ Reason: Your maximum cost-per-click (CPC) bid is lower than the minimum CPC bid recommended by the system for your keyword.
However, it claimed they weren't showing for an entirely different Adgroup than the one they were being used in. Almost as though the ADT takes one of the two words in the 2 word keyword phrase and tests that one. Fortunately, in real life the kws are indeed showing for the correct ads as I saw during my broad/phrase/exact test just now.
All should know that sometimes it reports this same message for words that are not marked "Inactive" (for the correct ad, BTW). As mentioned before, there are now two levels of inactivity, it appears:
a) The keywords clearly marked inactive
b) The keywords that has had no impressions in a while. Those just silently sit in your account and their status is unknown to you unless you test them manually.
I preferred the "Disabled" days when at least you knew to get rid of them as I know I've said before.
FWIW, I happen to rarely find single word kws useful to me. Perhaps the ADT works better for those?