Definition - Views in Amazon Search Results
The amount of views your sponsored product is receiving within the Search Results.
A view is registered if a customer lands within the searchresults of the specific searchterm, even if he does not see the actual product, eg. further below in the results.
This is not equal to Search Volume. If your sponsored product only appears on pages further behind, it will not get any impressions.
Possible Reasons for Low Impressions:
Wrong Sub-categorization of Product
In many cases Amazon may not deem the category registered for a product as fitting enough. In such cases it is advised to check which lowest sub-category your main competing products are part of.
Bids not High Enough
It may well be the case that other sellers are simply bidding more and thus have their products shown more often on the front pages of the search results. Amazon's "suggested bid" is in many cases slightly optimistic.
Budgets not High Enough
Amazon prefers keywords which have already generated clicks. This can often lead to the scenario that only few keywords will continue to be displayed and get clicks, so that in the end no budget remains for the other keywords.
Especially for (exact) adgroups in which you only have very relevant keywords it is therefore recommended to increase your budgets.
Low "Ad Score"
Amazon does not specifically show this score, but generally, Amazon, like all other advertising platforms, intends to show the most relevant results possible to searchers.
Things that go into that score are keyword indexation, as well as CTR & CR of your products and ads.
For the indexation, it is important to include all relevant keywords that you are trying target within your product listing content or backend.
No Impressions / Click / Sales History
As mentioned, Amazon will always prefer products that already have a certain history for a specific keyword. If you are starting to place ads for a new keyword, you may therefore have to increase your bid over-proportionally at the start to generate some first impressions and thus clicks.
According to many sources, a good Click-Through-Rate is the most important factor for a higher PPC-rank, as it is, of course, in Amazon's interest to generate as much revenue as possible from their PPC Plattform.
More History in other (Automatic) Campaign
It is for the same reason that manual campagins often receive no or fewer impressions than automatic campagins.
If a specific keyword is still active within two campaigns, Amazon will mainly choose the ad of the older campaign which generated more or any historical data.
You would therefore need to add the respective searchterms as negative keywords in that older campagin, so that the ad of the new campagins will start displaying.
New Campaign = Low Trust Score
Newly created campaigns do not have a significant "trust score" yet for about one month.
If there is a lot of (PPC) competition in a certain niche, it will often difficult to get a lot of impressions in that starting period.
Ad Requirement: Buy Box
Remember, Amazon will only run ads for product offers that have the Buy Box.