I have already tested with LINE on other OS and it works perfectly so I don't think the problem is the imageURL. (Just in case, I also try other URLs but the result is the same.) In terms of valid URL, I have opened both preview and original image URLs on browsers. it shows normally and both image file sizes are smaller than the requirement.
Recently, I also checked on MacOS and another Android device. The problem still occurs only in Android.
For now, I use Image carousel template instead of Image message as a workaround.
is your previewImageUrl valid? sometimes previewImageUrl and originalContentUrl need all valid so then the LINE app can show the image .