inserted images do not show up in post, only a placeholder does

[author_of_trusted_books]

I have just now submitted a question (same Board). 

As, only one attachment is permitted, and I had 4, so I used insert image option.

Neither in the draft stage, nor in the final post, those images showed up; instead, there were placeholders.

I may have done some mistake.

Can someone help me?

Thanks.