Yes that sounds like the direct method, and you are attaching to images to the thread rather than linking to them from another source or from the gallery.
(Tapatalk is an app mostly used on phones to make viewing the forum easier on the small screen).
According to the screen where you enter your attachments, they have to be 97.7Kb or less for JPG files. (There is also a max of 1024 x 768 resolution).
Is it possible only your first image is below that?