Warning Errors on my board outline in allegro while makeing a IDF

IDF requires closed loop geometry for all of the shapes that are exported (board outline, keep ins, keep outs, etc).  Allegro does not require a shape on Board Geometry / Outline.  Allegro's Export IDF command tries to assemble close shapes from the geometry on Board Geometry / Outline, and then determine which is the actual outline and which are cutouts (if any).  Any left over geometry is reported in the log file as you saw.  You should review the geometry at the location specified to determine if you need to fix the shape, delete the extra, or ignore it.

IDF Out processes each segment of the line and expects the outline to be contiguous.  

It sounds like what is happening to you is that the first line segment is determined to be unconnected and it is discarded.  The line segment that was connected at the other end is now unconnected.  The real problem was caused by the first segment.  The rest of the errors would not exist if the first error was fixed.

In general, to investigate these errors, work from the beginning of the idf_out.log file.  Open the log file using File > File Viewer.    Start at the top of the file and click on the X-Y coordinate of the line.  Clicking on the coordinate will move that point to the center of the Allegro window.  If necessary, zoom in or out.  If the Start coordinate is connected, click on the End coordinate.  If necessary, continue clicking on the coordinates in order until the open section is found, you may have to be zoomed in to see the disconnect.  Close the connection and repeat File > Export > IDF.