Help!
Why can't I see images that are sent on iMessage?
MacBook Air 11″, macOS 10.15
If you’re really running Sierra, upgrade to (at least) High Sierra, Mojave, or (maybe) Catalina, and try again.
How to upgrade to macOS High Sierra - Apple Support
If you post the MacBook Air model year ( 🍎 >About This Mac) we can look up whether this Mac sill run a version newer than High Sierra. A Mac running Sierra can run High Sierra.