The INSERT statement conflicted with the FOREIGN KEY??

<div> <div class="content">Keep getting the error:  The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Threads_Users".   table "dbo.Users", column 'uid'. Users table: <div>CREATE TABLE [dbo].[Users] (</div> <div>    [uid]       INT           IDENTITY (1, 1) NOT NULL,</div> <div>    [username]  VARCHAR (14)  NOT NULL,</div> <div>    [firstName] VARCHAR (20)  NULL,</div> <div>    [lastName]  VARCHAR (20)  NULL,</div> <div>    [gender]    VARCHAR (6)   NULL,</div> <div>    [picture]   VARCHAR (MAX) NULL,</div> <div>    CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ([uid] ASC) );</div> &l ...