Very strange.
Go to your (computer) file explorer system and find the image in your vault folder (where you place your vault in your computer system).
There try open/preview your image.
If image ok, back to Obsidian and try two things:
1 - open the help vault and place an image there;
2 - if everything works normally in help vault, return to your vault and check every extra: change theme to default; disable plugins; disable any css snippet; etc.