the URL of the image is giving 404 error
So the image doesn’t exist / has been taken down
but when I edit the image from the media menu the image is there
The image is saved locally on your computer in the temporary internet files. If you do a hard refresh (Shift + F5), the image will not be shown anymore.
what should I do?
Save the image, reupload it to any image cloud service (preferably imgur.com), use the URL generated by imgur.