A transaction that is still in Uncategorized Income or Uncategorized Expense cannot be marked reviewed – reviewing is your confirmation that the category is right. In the list the round check box is disabled for such rows; in the edit window the button is disabled with the note Categorize first to mark as reviewed, and if you force it the server replies Categorize first to mark as reviewed !. Pick a real category first, save, then mark it reviewed. Likewise, moving a reviewed transaction back to an Uncategorized category automatically clears its reviewed flag.