Error with Dropbox

Thank you @minnur ,
my WP version is 5.4.2 I use Ashe pro template

These are my media related plugins installed:
AJAX Thumbnail Rebuild
Folders
Image and video gallery from Google Drive (works fine)
Justified Gallery
WP File Manager

Notice that when I normally upload an image in Library, WP/Ashe automatically creates me some thumbnail files

This happens with Dropbox files imported by ExternalMedia plugin too (and it works fine)

When I import (with External media) an image from a GENERIC URL (with the specific button “Import from External URL” activated by settings with yhe checkbox “This plugin enables option to import files from remote URLs.”): everything goes fine, it creates file (example: ExternalLink_mmmmnnnnnn.jpg) and some thumbnails

When I import (with External media) an image with a DROPBOX SHARED LINK (with the specific button “Import from External URL” activated by settings with yhe checkbox “This plugin enables option to import files from remote URLs.”): it creates a file on server (example: ExternalLink_xxxyyyy.jpg), just 1 file without thumbnail files, with a dimension over than original, and if I try to put it on the Post… it give me warning at design time “This image has an empty alt attribute; its file name is ..” and nothing has shown in preview, neither if I try to open this image with a link on a new browser tab/window

By the way, the usage most of all I wanted was to link and view (in a Post) an image stored in Dropbox without import it
Confirm me that this is possible to do with External media

Thanks a lot

Ok @minnur thanks so much for support,
topic closed

By the way, congrats for your plugin that does his job well and clearly in spite of Dropbox links