Here are the primary reasons that your manual keywords might not have results:
No Data in Google Keyword Planner
In many cases, Google does not provide information for an exact keyword, but instead gives information for a near match. This is a result of Google's "bucketing" which combines keywords that have the same essential meaning and therefore should be shown the same results.
An example of this is the keyword "measuring brain waves" which has no exact result in the keyword planner. Instead, Google returns the keyword "measure brain waves".
Since we do not currently obtain data directly from the keyword planner, we are only able to provide exact match results for manual searches. Therefore, the keyword "measuring brain waves" will not show results in Long Tail Pro.
No Data from Our Data Providers
Since we no longer rely on Google AdWords for keyword data, we're now using two third party data providers for keywords. Unfortunately, our data providers do not have complete keyword coverage, especially for some international markets.
We're working on integrating an additional data provider with better international coverage. This is the development team's top priority, and we are currently testing a solution, but providing this data to a large number of users is challenging. We appreciate your patience while we complete this change.