Hello @adibablu ,
Make sure the Landscape does not have the Is Editor Only Actor option enabled, as actors marked as editor-only are excluded from packaged builds.
Also, verify that the map (and any sublevels containing the landscape) are included in the Packaging settings, and that the Landscape material is loading correctly.
Another thing worth checking is that the Build Configuration is set to Shipping when testing the packaged build.
I also found a post that mentions a possible solution to a very similar issue. The case is from Unreal Engine 5.3 rather than UE4, but it may still be useful as a reference.
Finally, if none of these suggestions help, what happens if you create a new project with a basic Landscape? Does the landscape appear correctly in the packaged build, or does it disappear there as well?
Hope it helps!