labatt, welcome to WebmasterWorld.
For purposes of the Knowledge Graph, Google, to define your business as a "local entity", is probably using prior Google Local, Google+, and Google My Business data that's been acquired by Google over time. It's assumed that you've also updated and verified, etc.
I don't know what kind of the reviews you are getting, how they were posted or what they say... but it sounds like Google might not trust your good reviews enough to feature them.
To get a handle on why not, it might be helpful to extrapolate from the organic backlink algorithm. Links and reviews/ recommendations are in a way analogous. In evaluating backlinks, Google tends to distrust "coordinated actions", because coordinated actions generally aren't natural.
Applying this same principle to user reviews, Google probably doesn't trust favorable reviews that come in clusters (as in close time proximity to each other, and are therefore probably coordinated). It would also mistrust reviews that come in large quantities, reviews that come from a common IP, reviews that were similar in wording to other reviews, reviews from people who've never posted reviews before... as well as well as reviews that are too negative or too positive, etc. Google has ways, of course, of comparing these clusters with news events, specials on the web, traffic to your site, etc.
I can imagine the above criteria weeding out some kinds of reviews that should be weeded out, probably also still allowing some junk to get through. Looking for other trust factors... though the status of Google+ isn't entirely clear, Google may still trust reviews from signed-in Google users over anonymous reviews... and Google would value a history of trust that might have been built up.
In your situation, I can imagine a scenario something like the following... and this may not be at all applicable, but just to think this through... I'm supposing the somehow you got a bad review, and that it may have been either natural or unnatural... who knows?... but at some point someone in your business may have noticed this and said, "Hey, let's get some good reviews to counter this."
Most benign face I can place on the likely follow-up would be that people in your company asked friends and customers to post some reviews, not telling them what to say, but they were friends eager to please, these all turned out to be favorable reviews... but too many of them came at the same time, from people who generally hadn't posted reviews before, etc etc... all arousing Google's suspicions, and Google decided not to display these. A complete guess, but likely. Possibly, someone might have hired reviewers... I don't know.
The rest are all five stars.
Well, that might make things worse. Too many five-star reviews is likely out of the norm, albeit I'm sure Google looks for other signals that might confirm the five-star quality they suggest. If any employees made recommendations, possibly on company computers, this would have raised more flags. It's also possible you simply got too many reviews.
You would have to look into how these favorable reviews came about, and look at them critically. I can't say what happened, and the weightings may be different for different kinds of businesses. Anyway, you see the nature of potential problems.
Going forward, you ultimately want to get a normal distribution of reviews, gradually, over time. You're probably best off to remind customers to review you, but not to specifically solicit reviews or to start a review campaign. That might also involve building up your organic and social presence on the web.
Here are some Google support guidelines that may in fact be in transition, but which might be helpful....
Review and photo policies [
support.google.com...]
