On the “Standard” tab there is an icon called “Database Range”. This is used to control the time period used for document searches. For example, if it’s set to “Current Calendar Year” it only searches through records created since the 1st January of the current year. The longer the time span the longer searches take. Equally a shorter time span speeds up the search, but ensure that it is wide enough to find the documents you are looking for.
Note that Last Calendar Years option will suddenly remove access to 12 months of data on 1st January unless range is changed.
Also note another reason why you might not be seeing all the documents expected is shown in DOCUMENTS below.