iMessage issue - images from old text conversations (when I had an Android) do not load

I moved from Android to iOS back in January. Ever since then, I have been unable to access images that I sent via text when I had my old phone. It appears as it does in the screenshot: a random filename, "JPEG Image · x KB". If I click on it, it "starts" to download but just says "Zero KB of x KB" and never loads any further. However, after I do that, a new prompt appears. If I look at the conversation info, right below "Delete and Block this Conversation", it says "1 image in iCloud - Download". But when I click on that, it says "Downloading" for a split second, and then it just loops back around to the first screenshot, as if I hadn't clicked on the image.

See these screenshots:

Things I have tried that didn't work:

• Turning "Messages in iCloud" off and on multiple times
• Turning iMessage off and on
• Turning off everything under Siri & Search > Messages and turning it back on

This occurs on both my iPhone and my Mac, both of which have the latest updates installed (Sonoma 14.4.1 and iOS 17.4.1, respectively).