I believe you’ve got something wrong with the image path:
This is how I’ve managed to view the image:
[center][img]https://imgpile.com/images/5UsZtG.png[/img][/center]
This is your code in your thread of a random case I tried:
[center][img]https://imgpile.com/i/5UsZtG[/img][/center]
This is your case in the OP, using the proper link:
[center][img width=400]https://i.imgur.com/ZX4vRam.jpeg[/img][/center]
Your code:
[center][img]https://imgur.com/a/PY5VYr9[/img][/center]
Note: No quotes should go in the BBCode structure either.
In both cases, I just viewed the image in a browser via the url in your code, right-clicked on the image, and copied the "image link" (you should be able to get the same from your image environment directly, from the BBCode button on imgur for example).