I put two archiveArtifacts steps in a declarative Jenkinsfile but only the files archived by the first step show up in the Jenkins UI.
The build directory in the Jenkins master then contains both "archive.zip" with files from the first step, and "archive.zip.writing.zip" with files from the second step. I think the tempArchive.renameTo(archive); call in ZipStorage failed. There is a comment "TODO support updating entries", so this is apparently a known problem.
However, if this kind of thing is not supported, then I think the build should at least have failed with an explanation in Console Output. I got no warnings there, and the build succeeded: