The Application log tab, in the lower-right panel, records what LanSend does as you work: messages sent, status checks, and any problems it runs into. It is the first place to look when something does not behave as expected.

Each row has four columns: Time, Level, Category, and Message. Levels run from Debug through Info, Warning, Error, and Fatal.
A search box filters by text, the level buttons limit the list to the levels you care about, and the Category dropdown filters to one area of the program. A status line shows how many of the total entries match.
To control how much the log records, and to write it to a file as well, see the Logging preferences.