Hello @JulieK072 ,
Are the images not showing in the email editor, or in the library? If working in the editor, is it that the images don't appear in the lefthand menu, or that they're not appearing in little Library window when Replacing / Inserting an image into an image block? If the issue is that it's simply not appearing in the lefthand menu, you may need to refresh your browser screen. If the image isn't appearing the little Library window or the actual Library tab post-upload, it's most likely a caching error.
Here are some general best practices for deliverability.
Deliverability can have a lot of variables, from elements on our side, on your side, on the recipient's side, and in their email system company's side. It's also a generally good idea to set up additional authentication for your emails - whether that's through us if you have a free domain (e.g. Gmail, Yahoo, AOL, etc.) or via self-authentication if you have your own domain (such as through a business or other organization).
If you'd like to learn more about safelisting, and what it entails:
If you're wanting more in-depth, specialized insight on your current deliverability, it'd be worth speaking with one of our Deliverability agents.